Advertisement
Trends in Endocrinology & Metabolism
This journal offers authors two options (open access or subscription) to publish research

Integration of androgen hormones in endometrial cancer biology

Open AccessPublished:July 22, 2022DOI:https://doi.org/10.1016/j.tem.2022.06.001

      Highlights

      • As clinical management of advanced and recurrent endometrial cancer (EC) moves closer to molecularly targeted therapy, a better understanding of endometrial tumor biology is needed.
      • Epidemiological studies associate androgens with greater EC risk, the expression of the androgen receptor, on the other hand, with less aggressive primary disease.
      • The endometrial tumor tissue and the distinctly altered microbiota can contribute to the pool of bioactive androgens available to the tumor.
      • The biological effect of androgen signaling differs throughout tumor evolution as it integrates in a complex signaling network deciding cell fate.
      Endometrial cancer (EC) is a gynecological pathology that affects the uterine inner lining. In recent years, genomic studies revealed continually evolving mutational landscapes of endometrial tumors that hold great potential for tailoring therapeutic strategies. This review aims to broaden our knowledge of EC biology by focusing on the role of androgen hormones. First, we discuss epidemiological evidence implicating androgens with EC pathogenesis and cover their biosynthesis and metabolism to bioactive 11-oxyandrogens. Next, we explore the endometrial tumor tissue and the altered microbiota as alternative sources of androgens and their 11-oxymetabolites in EC patients. Finally, we discuss the biological significance of androgens' genomic and nongenomic signaling as part of a medley of pathways ultimately deciding the fate of cells.

      Keywords

      Endometrial cancer today

      Endometrial cancer (EC) is a gynecological, predominantly postmenopausal pathology that arises in the inner epithelial lining of the uterus. In 2020, the age-standardized incidence and mortality rate were 8.7 and 1.8 per 100 000 population, respectively [
      • Sung H.
      • et al.
      Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.
      ]. Worldwide, the cumulative risk of the disease until the age of 74 is 1.05%; however, this risk is doubled in countries with higher sociodemographic index, particularly in Northern America and Europe [
      • Sung H.
      • et al.
      Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.
      ]. Notably, a decrease in the disability-adjusted life years (DALYs) index (see Glossary), was observed globally during the past decade [
      • Kocarnik J.M.
      • et al.
      Cancer incidence, mortality, years of life lost, years lived with disability, and disability-adjusted life years for 29 cancer groups from 2010 to 2019: a systematic analysis for the Global Burden of Disease Study 2019.
      ]. Nonetheless, the management of advanced, metastatic, and recurrent EC still remains challenging.
      EC comprises distinct types, of which the endometrioid type accounts for approximately 80% of cases. Nonendometrioid types include serous EC, clear-cell EC, carcinosarcoma, as well as other rarer types [
      • Board W.F.G.T.
      Female Genital Tumours: WHO Classification of Tumours.
      ]. Endometrioid EC is further categorized into low and high grade, using criteria from the International Federation of Gynaecological Oncology (FIGO). Low-grade endometrioid tumors are generally associated with a favorable clinical outcome, whereas high-grade endometrioid tumors and nonendometrioid tumor types are associated with higher recurring frequency and a worse clinical outcome. In addition to determining the EC type, the newest World Health Organization (WHO) classification [
      • Board W.F.G.T.
      Female Genital Tumours: WHO Classification of Tumours.
      ] encourages molecular classification of endometrial tumors into four distinct categories identified by The Cancer Genome Atlas (TCGA) Research Network [
      • Kandoth C.
      • et al.
      Integrated genomic characterization of endometrial carcinoma.
      ]; these include DNA polymerase epsilon catalytic subunit (POLE)-ultramutated, microsatellite instability (MSI)-hypermutated, copy-number (CN) low, and CN high.
      The cornerstone of EC treatment is surgery, or treatment with progestins for younger patients that want to preserve fertility [
      • Colombo N.
      • et al.
      ESMO-ESGO-ESTRO Consensus Conference on Endometrial Cancer: diagnosis, treatment and follow-up.
      ]. The EC grade and stage determine the surgical approach. Generally, for lower grade and lower stage EC, surgery encompasses total hysterectomy and bilateral salpingo-oophorectomy, carried out preferably by minimally invasive surgery. For advanced EC, radical cytoreductive surgery with lymphadenectomy is performed [
      • Colombo N.
      • et al.
      ESMO-ESGO-ESTRO Consensus Conference on Endometrial Cancer: diagnosis, treatment and follow-up.
      ,
      • Concin N.
      • et al.
      ESGO/ESTRO/ESP guidelines for the management of patients with endometrial carcinoma.
      ]. High-risk patients receive adjuvant therapy, involving either radiotherapy, chemotherapy, or a combination, as well as hormonal therapy [
      • Concin N.
      • et al.
      ESGO/ESTRO/ESP guidelines for the management of patients with endometrial carcinoma.
      ].

      Mutational landscape of EC and its importance in tomorrow's EC management

      In recent years, several large-scale whole-genome sequencing (WGS) analysis efforts have provided valuable insights into the mutational landscape of different cancer types, including EC [
      • Kandoth C.
      • et al.
      Integrated genomic characterization of endometrial carcinoma.
      ,
      • Zehir A.
      • et al.
      Mutational landscape of metastatic cancer revealed from prospective clinical sequencing of 10,000 patients.
      ,
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ]. These efforts have opened a new window of therapeutic approaches tailored to the tumor-specific genomic fingerprint.
      A landmark study from TCGA involving more than 11 000 cancer patients, including 373 EC cases, has identified four distinct molecular categories of endometrial tumors [
      • Kandoth C.
      • et al.
      Integrated genomic characterization of endometrial carcinoma.
      ]. Endometrioid EC is categorized into POLE-ultramutated, MSI-hypermutated, and CN low endometrial tumors. Serous EC and the most aggressive endometrioid tumors are grouped into CN high molecular category of endometrial tumors. In addition to TCGA study, which primarily involved primary tumors, two recent studies were performed at the Memorial Sloan Kettering Cancer Center, namely the Memorial Sloan Kettering (MSK)-IMPACT study, involving >10 000 patients, among them 218 were EC patients, and the MSK-Metastatic events and Tropism (MET) study, involving >25 000 patients, among them 1315 were EC patients, predominantly sequenced advanced and metastatic, usually heavily pretreated tumors [
      • Zehir A.
      • et al.
      Mutational landscape of metastatic cancer revealed from prospective clinical sequencing of 10,000 patients.
      ,
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ]. In general, both the studies showed that advanced endometrial tumors tend to have higher mutation frequency, compared with primary tumors from TCGA database. In Figure 1, we summarize the most frequent somatic mutations, the tumor mutational burden (TMB), and the chromosomal instability, inferred by the fraction of genome altered (FGA), of EC types that were included in the MSK-MET study [
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ].
      Figure 1
      Figure 1Genomic landscape of endometrial cancer (EC).
      Genomic profile of endometrioid, hypermutated endometrioid, serous EC, and carcinosarcoma based on the MSK-MET study is represented (data extracted from [
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ]). Note the higher frequency of somatic mutations and tumor mutational burden (TMB) in hypermutated endometrioid, compared with other EC types. In all EC types, higher percentage of the fraction of genome altered (FGA) is observed in metastatic tumors compared with primary tumors. All types, especially endometrioid, display frequent mutations in the PI-3-kinase/AKT pathway. The pathway is activated by growth factors, that activate a receptor tyrosine kinase (RTK); next, PI-3-kinase (composed of subunits p85 and p110) forms a second messenger phosphatidylinositol (3,4,5)-triphosphate (PIP3) from PIP2; PTEN phosphatase dephosphorylates PIP3. PIP3 recruits the serine/threonine kinase AKT to the plasma membrane, where it is activated through phosphorylation. Activated AKT promotes glucose metabolism, cell growth, and proliferation. In EC, mutations in p85 and p110α subunits (encoded by PIK3R1 and PIK3CA, respectively) as well as inactivating mutations in PTEN, contribute to enhanced activation of the pathway. Serous EC and carcinosarcoma are characterized by high frequency of inactivating TP53 mutations. The p53 pathway is at the center of a complex web of interactions that senses stress signals, such as DNA damage and radiation through ATM and ATR, resulting in cell cycle arrest or apoptosis. Created with BioRender (https://biorender.com/). Abbreviations: ATM, ataxia telangiectasia mutated; ATR, ataxia telangiectasia and Rad3 related.
      Of note, genes involved in the phosphatidylinositol 3 (PI-3)-kinase/AKT pathway are among the most frequently mutated genes in both endometrioid and MSI-hypermutated endometrioid EC (Figure 1) [
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ,
      • Sanchez-Vega F.
      • et al.
      Oncogenic signaling pathways in The Cancer Genome Atlas.
      ]. The nonendometrioid tumors, serous EC and carcinosarcoma, display pathognomonic mutations in the tumor suppressor TP53 gene, as well as mutations in the PI-3-kinase/AKT pathway. In addition, both endometrioid and nonendometrioid EC display mutations in genes regulating chromatin organization and accessibility, such as ARID1A gene. Moreover, advanced endometrial tumors are characterized with higher chromosomal instability compared with primary tumors. In the case of endometrioid and MSI-hypermutated endometrioid EC, higher chromosomal instability is associated with greater metastatic burden [
      • Nguyen B.
      • et al.
      Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
      ]. Not surprisingly, these genomic alterations also result in changes in DNA acetylation and methylation status as well as changes at protein and phosphoprotein levels, altogether altering whole cellular processes in the tumor [
      • Dou Y.
      • et al.
      Proteogenomic characterization of endometrial carcinoma.
      ].
      Taken together, these studies have helped in identifying the molecular fingerprint of distinct EC types. Nonetheless, even though a great proportion of endometrial tumors harbors at least one genomic alteration [
      • Soumerai T.E.
      • et al.
      Clinical utility of prospective molecular characterization in advanced endometrial cancer.
      ,
      • Bailey M.H.
      • et al.
      Comprehensive characterization of cancer driver genes and mutations.
      ], currently, only the MSI status is exploited as an actionable alteration in advanced EC. More specifically, two of five FDA-approved chemotherapy agents for EC effectively target a specific ligand, programmed death ligand 1 (PD-1), that is overexpressed in MSI-hypermutated endometrial tumors, compared with microsatellite stable tumors [
      • Ott P.A.
      • et al.
      Safety and antitumor activity of pembrolizumab in advanced programmed death ligand 1–positive endometrial cancer: results from the KEYNOTE-028 study.
      ,
      • Oaknin A.
      • et al.
      Safety and antitumor activity of dostarlimab in patients with advanced or recurrent DNA mismatch repair deficient/microsatellite instability-high (dMMR/MSI-H) or proficient/stable (MMRp/MSS) endometrial cancer: interim results from GARNET—a phase I, single-arm study.
      ]. In the following years, however, greater utilization of prospective clinical sequencing, as well as an increase in the number of molecularly driven clinical trials and approved molecular targeted therapies, is expected to move EC management beyond the variables of tumor histology and grade.

      Androgens' integration in EC biology

      Epidemiological evidence implicates androgens with EC risk

      Androgens are steroid hormones with biological effects on both pre- and postmenopausal female physiology. The levels of these hormones are negligible until adrenarche, after which they start to rise gradually, reach a peak by the mid-20s, and then start to decline gradually [
      • Labrie F.
      • et al.
      DHEA and the intracrine formation of androgens and estrogens in peripheral target tissues: its role during aging.
      ]. Throughout the female reproductive ages, both the adrenals, more specifically the inner layer of the adrenal cortex, that is, zona reticularis, and the gonads, more specifically, the thecal cells surrounding the ovarian follicles, contribute to androgen production [
      • Longcope C.
      Adrenal and gonadal androgen secretion in normal females.
      ]. With aging, an involution of the adrenal zona reticularis and a drastic reduction in the number of ovarian follicles take place, altogether causing a reduction of androgen synthesis [
      • Longcope C.
      Adrenal and gonadal androgen secretion in normal females.
      ]. Nonetheless, both glands remain an important source of androgens post menopause [
      • Labrie F.
      • et al.
      DHEA and the intracrine formation of androgens and estrogens in peripheral target tissues: its role during aging.
      ]. Apart from classical androgens, the adrenal glands also produce androgen metabolites that share an oxygen atom at the C11 position, called 11-oxyandrogens (Figure 2). These 11-oxymetabolites are particularly interesting in postmenopausal female physiology as their levels, contrary to classical androgens, do not decline with age (Table 1) [
      • Nanba A.T.
      • et al.
      11-oxygenated C19 steroids do not decline with age in women.
      ,
      • Caron P.
      • et al.
      A quantitative analysis of total and free 11-oxygenated androgens and its application to human serum and plasma specimens using liquid-chromatography tandem mass spectrometry.
      ].
      Figure 2
      Figure 2Adrenal androgen synthesis and peripheral activation.
      The innermost layer of the adrenal cortex synthesizes C19 androgens and a set of androgen metabolites, 11-oxyandrogens. The precursors, dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S), androstenedione (A4), 11β-hydroxyandrostenedione (11β-OH-A4), as well as smaller quantities of bioactive androgens, testosterone (T), and 11β-hydroxytestosterone (11β-OH-T), travel via the systemic circulation bound to plasma proteins and eventually reach target tissues (broken lines represent diffusion). Here, DHEA-S, DHEA, A4, and T give rise to 5α-dihydrotestosterone (DHT), the biologically most potent androgen. Likewise, the 11-oxyandrogens 11β-OH-A4 and 11β-OHT are eventually converted to bioactive androgens, such as 11-keto-DHT (11-K-DHT). Active androgens bind to the androgen receptor (AR); the ligand–receptor complex binds to androgen response elements (AREs) on DNA and eventually induces transcriptional changes in androgen-responsive genes. Lower panel (left): AR expression profile in normal human tissues shown in log2 (TPM+1) scale based on http://gepia.cancer-pku.cn (accessed in May 2022). Created with BioRender (https://biorender.com/). Abbreviations: 11-K-A4, 11-ketoandrostenedione; 11-K-T, 11-ketotestosterone; AKR1C3, aldo-keto reductase family 1 member 3; CYP11A1, cytochrome P450 cholesterol side chain cleavage; CYP11B1, cytochrome P450 11β-hydroxylase; CYP17A1, 17α-hydroxylase/17,20 lyase; HSD3B2, 3β-hydroxysteroid dehydrogenase type 2; HSD11B2, 11β-hydroxysteroid dehydrogenase type 2; HSD17B1, 17β-hydroxysteroid dehydrogenase type 1; OH, hydroxy; SRD5A, steroid 5α-reductase; STS, sulfatase; SULT2A1, steroid sulfotransferase type 2A1; TPM, transcript per million.
      Table 1Serum concentrations of major androgens and 11-oxyandrogens in healthy pre- and postmenopausal women
      Abbreviations: 11-K-A4, 11-ketoandrostenedione; 11-K-T, 11-ketotestosterone; 11-OH-A4, 11β-hydroxyandrostenedione; 11-OH-T, 11-hydroxytestosterone; DHEA, dehydroepiandrosterone; DHEA-S, DHEA sulfate.
      Data are expressed as median (interquartile ranges) and were extracted from [17].
      Steroid hormoneConcentration (nM)
      Premenopausal women (n = 100; aged 20–40 years)Postmenopausal women (n = 100; aged 60–80 years)
      DHEA-S3155.17 (1929.78–5603.18)1051.47 (604.02–1461.95)
      DHEA8.04 (5.37–13.97)2.74 (1.80–4.65)
      Androstenedione (A4)3.46 (2.65–5.22)1.19 (0.80–1.78)
      Testosterone1.04 (0.76–1.39)0.66 (0.49–1.07)
      11β-OH-A45.69 (3.90–8.63)6.48 (4.66–9.56)
      11-K-A41.23 (0.87–1.83)1.13 (0.77–1.53)
      11β-OH-T0.46 (0.30–0.76)0.66 (0.43–0.92)
      11-K-T0.86 (0.63–1.26)0.93 (0.73–1.22)
      a Abbreviations: 11-K-A4, 11-ketoandrostenedione; 11-K-T, 11-ketotestosterone; 11-OH-A4, 11β-hydroxyandrostenedione; 11-OH-T, 11-hydroxytestosterone; DHEA, dehydroepiandrosterone; DHEA-S, DHEA sulfate.
      b Data are expressed as median (interquartile ranges) and were extracted from [
      • Nanba A.T.
      • et al.
      11-oxygenated C19 steroids do not decline with age in women.
      ].
      Biologically active androgens, such as testosterone (T) and 5α-dihydrotestosterone (DHT), act on target tissues primarily via the androgen receptor (AR). Likewise, some 11-oxyandrogens, such as 11-keto-T (11-K-T) and 11-keto-DHT (11-K-DHT), have similar affinity for binding to AR as the classical hormones [
      • Storbeck K.-H.
      • et al.
      11β-Hydroxydihydrotestosterone and 11-ketodihydrotestosterone, novel C19 steroids with androgenic activity: a putative role in castration resistant prostate cancer?.
      ,
      • Rege J.
      • et al.
      11-ketotestosterone is the dominant circulating bioactive androgen during normal and premature adrenarche.
      ,
      • Pretorius E.
      • et al.
      11-ketotestosterone and 11-ketodihydrotestosterone in castration resistant prostate cancer: potent androgens which can no longer be ignored.
      ,
      • Handelsman D.J.
      • et al.
      Bioactivity of 11 keto and hydroxy androgens in yeast and mammalian host cells.
      ]. Henceforth, the term bioactive androgens will be used for both classical androgens and 11-oxyandrogens.
      AR belongs to the nuclear receptor superfamily of proteins and comprises an N-terminal regulatory domain, containing two activation function (AF) sequences, namely AF-1 and AF-5, a DNA-binding domain (DBD), a hinge region, containing nuclear localization signal sequence, a ligand-binding domain, containing AF-2 and nuclear export signal sequence, and finally a C-terminal domain [
      • Brinkmann A.O.
      • et al.
      Structure and function of the androgen receptor.
      ]. While inactive, AR is maintained in the cytosol by molecular chaperones, such as heat shock proteins, co-chaperones, and cytoskeletal proteins. Binding of AR to its natural ligand triggers dissociation of the receptor from chaperones and induces conformational changes that enable AR dimerization and translocation to the nucleus. Here, the receptor–ligand complex binds to androgen response elements (AREs) located at the promoter region of target genes, which ultimately alters gene transcription, thus evokes a biological response. In the premenopausal endometrium, AR is predominantly expressed in stromal cells and it is involved in several processes, such as endometrial preparation to a possible pregnancy and endometrial repair following menstruation [
      • Mertens H.J.M.M.
      • et al.
      Androgen, estrogen and progesterone receptor expression in the human uterus during the menstrual cycle.
      ,
      • Marshall E.
      • et al.
      In silico analysis identifies a novel role for androgens in the regulation of human endometrial apoptosis.
      ,
      • Gibson D.A.
      • et al.
      Regulation of androgen action during establishment of pregnancy.
      ]. AR expression is maintained in the postmenopausal endometrium as well [
      • Kamal A.M.
      • et al.
      Androgen receptors are acquired by healthy postmenopausal endometrial epithelium and their subsequent loss in endometrial cancer is associated with poor survival.
      ].
      In the case of EC, the role of androgens, and particularly that of their 11-oxymetabolites, is not clear. Generally, androgens are regarded as potential risk factors as they represent an estrogen source to the endometrial tumor, through aromatization of T to estradiol; this conversion takes place primarily in peripheral fatty depots [
      • Siiteri P.K.
      Adipose tissue as a source of hormones.
      ]. Several studies investigated the correlation between androgens' systemic levels and EC risk. For instance, the androgen precursor, dehydroepiandrosterone-sulfate (DHEA-S), and the androgen androstenedione (A4) are inconclusively associated with EC; some studies regard them as EC risk factors [
      • Lukanova A.
      • et al.
      Circulating levels of sex steroid hormones and risk of endometrial cancer in postmenopausal women.
      ,
      • Michels K.A.
      • et al.
      Postmenopausal androgen metabolism and endometrial cancer risk in the Women's Health Initiative Observational Study.
      ], whereas others do not find an association [
      • Clendenen T.V.
      • et al.
      Premenopausal circulating androgens and risk of endometrial cancer: results of a prospective study.
      ]. Furthermore, higher premenopausal T levels associate with a greater risk of developing EC post menopause [
      • Clendenen T.V.
      • et al.
      Premenopausal circulating androgens and risk of endometrial cancer: results of a prospective study.
      ]. Notably, a possible limitation of these studies is that they take into account hormone levels at a single time period, at which a patient is enrolled into a study. In recent years, several studies reported genetically predicted steroid hormone levels, likely reflecting levels to which an individual is exposed throughout lifetime, and associated them with a number of pathologies, including EC. More specifically, two Mendelian randomization studies involving participants of European ancestry, including over 12 000 EC patients from the UK Biobank, correlated higher genetically determined levels of bioavailable, that is, free T with adverse effects on both endometrioid and nonendometrioid endometrial tumors [
      • Ruth K.S.
      • et al.
      Using human genetics to understand the disease impacts of testosterone in men and women.
      ,
      • Mullee A.
      • et al.
      Testosterone, sex hormone-binding globulin, insulin-like growth factor-1 and endometrial cancer risk: observational and Mendelian randomization analyses.
      ].
      Another association between androgen levels and EC risk can be indirectly seen in patients with higher body mass index (BMI), which may have elevated systemic T levels as well [
      • Danforth K.N.
      • et al.
      The association of plasma androgen levels with breast, ovarian and endometrial cancer risk factors among postmenopausal women.
      ,
      • Allen N.E.
      • et al.
      Endogenous sex hormones and endometrial cancer risk in women in the European Prospective Investigation into Cancer and Nutrition (EPIC).
      ]. Indeed, several large-scale studies have confirmed a positive correlation between higher BMI and EC risk [
      • O’Mara T.A.
      • et al.
      Identification of nine new susceptibility loci for endometrial cancer.
      ,
      • Bhaskaran K.
      • et al.
      Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5.24 million UK adults.
      ,
      • Park I.S.
      • et al.
      Risk of female-specific cancers according to obesity and menopausal status in 2.7 million Korean women: similar trends between Korean and Western women.
      ]. The association between high BMI, T levels, and EC risk is also evident in patients with polycystic ovary syndrome (PCOS) [
      • Yin W.
      • et al.
      Association between polycystic ovary syndrome and cancer risk.
      ,
      • Taylor A.
      • et al.
      11-oxyandrogen concentrations in adolescents with polycystic ovary syndrome (PCOS).
      ].
      In continuation, we will explore the adrenal androgen biosynthesis and androgen activation in peripheral target tissues in a physiological state and explore the endometrial tumor tissue and microbiota as additional sources that might contribute to the androgen pool in EC patients.

      Androgen synthesis and peripheral activation

      Androgen adrenal synthesis

      The adrenal cortex is a de novo source of androgen precursors, dehydroepiandrosterone (DHEA) and DHEA-S, androgens, A4, and T, as well as 11-oxyandrogens, 11β-hydroxy-androstenedione (11β-OH-A4), and 11β-hydroxytestosterone (11β-OH-T) (Figure 2). Steroidogenesis begins with cholesterol, which is transferred from the cytoplasm to the inner mitochondrial membrane in a rate-limiting step, mediated by the steroidogenic acute regulatory protein (StAR) [
      • Miller W.L.
      • Auchus R.J.
      The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders.
      ]. The next, likewise rate-limiting step involves sequential hydroxylation at C22 and C20 and cleavage between C20 and C22, resulting in the formation of pregnenolone, the C21 parent compound for all steroid hormones. This reaction is mediated by the cholesterol side chain cleavage enzyme CYP11A1, a mitochondrial cytochrome P450 mixed-function oxidase [
      • Shimizu K.
      • et al.
      The transformation of 20α-hydroxycholesterol to isocaproic acid and C21 steroids.
      ]. Pregnenolone is next converted to DHEA, the initial C19 steroid, by the CYP17A1 enzyme [
      • Zuber Mauricio X.
      • et al.
      Expression of bovine 17α-hydroxylase cytochrome P-450 cDNA in nonsteroidogenic (COS 1) cells.
      ,
      • Auchus R.J.
      • et al.
      Cytochrome b5 augments the 17,20-lyase activity of human P450c17 without direct electron transfer.
      ].
      The nascent DHEA can then be converted into a sulfated androgen precursor, DHEA-S by the sulfotransferase enzyme SULT2A1, or to A4 by the 3β-hydroxysteroid dehydrogenase/Δ5Δ4 isomerase type 2 (HSD3B2) enzyme in the adrenal glands, or HSD3B1 in peripheral tissues [
      • Labrie F.
      • et al.
      Structure, function and tissue-specific gene expression of 3β-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase enzymes in classical and peripheral intracrine steroidogenic tissues.
      ]. A4 is further converted to T by the action of 17β-HSD type 5 (HSD17B5), a member of the aldo-keto reductase family, better known as AKR1C3 [
      • Nakamura Y.
      • et al.
      Type 5 17β-hydroxysteroid dehydrogenase (AKR1C3) contributes to testosterone production in the adrenal reticularis.
      ]. The formed DHEA-S, DHEA, A4, and T can then enter into systemic circulation, where the latter three associate mainly with steroid hormone binding globulin (SHBG), whereas DHEA-S with albumin. Alternatively, A4 and T can be hydroxylated to 11β-OH-A4 and 11β-OH-T, respectively, by the adrenal-specific cytochrome P450 11β-hydroxylase (CYP11B1) enzyme [
      • Mornet E.
      • et al.
      Characterization of two genes encoding human steroid 11β-hydroxylase (P-45011β)*.
      ].

      Peripheral activation of adrenal androgens

      The adrenal DHEA-S, DHEA, A4, T, as well as 11-OH-A4 and 11-OH-T reach peripheral target tissues, such as adipose tissue, genital skin, and ovaries through the systemic circulation. Here, they are converted to biologically active molecules with high affinity to AR (Figure 2) [
      • Labrie F.
      • et al.
      DHEA and the intracrine formation of androgens and estrogens in peripheral target tissues: its role during aging.
      ,
      • Blouin K.
      • et al.
      Pathways of adipose tissue androgen metabolism in women: depot differences and modulation by adipogenesis.
      ].
      The peripheral utilization of the most abundant androgen precursor, DHEA-S, requires the presence of transporters, such as organic anion-transporting polypeptides (OATPs), encoded by the evolutionarily conserved solute carrier for organic anions (SLCO) family [
      • Rižner T.L.
      • et al.
      The importance of steroid uptake and intracrine action in endometrial and ovarian cancers.
      ]. The entry of other neutral steroid molecules, such as DHEA, A4, and T, is thought to occur by simple diffusion through the membrane; this assumption, however, has been challenged by several studies, that indicated the involvement of transporters in sex steroid uptake [
      • Okamoto N.
      • et al.
      A membrane transporter is required for steroid hormone uptake in Drosophila.
      ,
      • Sissung T.M.
      • et al.
      Differential expression of OATP1B3 mediates unconjugated testosterone influx.
      ,
      • Hammes A.
      • et al.
      Role of endocytosis in cellular uptake of sex steroids.
      ]. Once inside cells, DHEA-S is converted to DHEA by the action of the steroid sulfatase (STS) enzyme, DHEA next to A4 by HSD3B enzymes, A4 further to T, by the action of AKR1C3 in the peripheral tissue, or HSD17B3 enzyme in the testis. Finally, T is converted to the biologically most potent androgen DHT, by steroid 5α-reductases (SRD5A) type 1, 2, and 3 [
      • Han Y.
      • et al.
      Crystal structure of steroid reductase SRD5A reveals conserved steroid reduction mechanism.
      ]. Similar to classical androgens, the utilization of 11β-OH-A4 and 11β-OH-T by peripheral organs most likely requires transporters, as well as the expression of HSD11B2, AKR1C3, and SDR5A enzymes, eventually leading to the formation of the equally potent DHT homolog, 11-K-DHT [
      • Storbeck K.-H.
      • et al.
      11β-Hydroxydihydrotestosterone and 11-ketodihydrotestosterone, novel C19 steroids with androgenic activity: a putative role in castration resistant prostate cancer?.
      ,
      • Barnard M.
      • et al.
      11-Oxygenated androgen precursors are the preferred substrates for aldo-keto reductase 1C3 (AKR1C3): implications for castration resistant prostate cancer.
      ].

      Additional peripheral sources of bioactive androgens in EC

      The endometrial tumor tissue as a source of bioactive androgens

      The endometrial tumor tissue is equipped with the necessary enzymatic machinery to be considered a relevant source of biologically active androgens from androgen and 11-oxyandrogen precursors. The expression of several key enzymes involved in androgen metabolism, such as AKR1C and SRD5A enzymes, has been investigated in endometrial tumor tissue by our group and others [
      • Sinreih M.
      • et al.
      Altered expression of genes involved in progesterone biosynthesis, metabolism and action in endometrial cancer.
      ,
      • Hojnik M.
      • et al.
      AKR1C3 is associated with better survival of patients with endometrial carcinomas.
      ,
      • Ito K.
      • et al.
      Expression of androgen receptor and 5α-reductases in the human normal endometrium and its disorders.
      ,
      • Rižner T.L.
      • et al.
      AKR1C1 and AKR1C3 may determine progesterone and estrogen ratios in endometrial cancer.
      ,
      • Šmuc T.
      • Rižner T.L.
      Aberrant pre-receptor regulation of estrogen and progesterone action in endometrial cancer.
      ,
      • Hevir-Kene N.
      • Rižner T.L.
      The endometrial cancer cell lines Ishikawa and HEC-1A, and the control cell line HIEEC, differ in expression of estrogen biosynthetic and metabolic genes, and in androstenedione and estrone-sulfate metabolism.
      ]. For the purpose of this review, we have extracted the gene expression of key steroid hormone transporters and enzymes involved in androgen metabolism from TCGA's Pan-Cancer Atlas study [
      • Chang K.
      • et al.
      The Cancer Genome Atlas Pan-Cancer analysis project.
      ], available through the cBioPortal [
      • Cerami E.
      • et al.
      The cBio cancer genomics portal: an open platform for exploring multidimensional cancer genomics data.
      ,
      • Gao J.
      • et al.
      Integrative analysis of complex cancer genomics and clinical profiles using the cBioPortal.
      ] (Figure 3).
      Figure 3
      Figure 3Peripheral sources of bioactive androgens in endometrial cancer (EC).
      In EC, the adipose tissue, the microbiota, and the endometrial tumor tissue contribute to the pool of bioactive androgens. The lower panel represents logarithmic z score expression of genes involved in the androgen metabolism in endometrial tumor tissues, relative to normal samples (data extracted from [
      • Chang K.
      • et al.
      The Cancer Genome Atlas Pan-Cancer analysis project.
      ]). Of note, the greater expression of several SLCOs might account for a greater influx of steroid precursors in both endometrioid and serous EC tissues, whereas the higher expression of SRD5A isoforms 1 and 3 in endometrioid tumors might contribute to enhanced DHT and 11-K-DHT formation. Notably, the absence of CYP11B1 expression suggests that endometrial tumors cannot metabolize androgens to 11-oxyandrogens. Locally synthesized and systemic androgens evoke biological responses in the endometrial tumor. Created with BioRender (https://biorender.com/).
      Interestingly, both endometrioid and nonendometrioid EC display higher expression of several SLCO genes coding for transporters with broad substrate specificity, compared with normal endometrial tissues [
      • Chang K.
      • et al.
      The Cancer Genome Atlas Pan-Cancer analysis project.
      ,
      • Pavlič R.
      • et al.
      Altered profile of E1-S transporters in endometrial cancer: lower protein levels of ABCG2 and OSTβ and up-regulation of SLCO1B3 expression.
      ]. We have recently showed that upregulation of several OATPs might account for a greater influx of steroid precursors, including DHEA-S, in the endometrial tumor [
      • Pavlič R.
      • et al.
      Altered profile of E1-S transporters in endometrial cancer: lower protein levels of ABCG2 and OSTβ and up-regulation of SLCO1B3 expression.
      ]. Another key enzyme in the androgen metabolism is AKR1C3, whose overexpression has been suggested to contribute to the androgen pool in a number of pathologies, including breast cancer, PCOS, and castrate-resistant prostate cancer [
      • Penning T.M.
      • et al.
      Structural and functional biology of aldo-keto reductase steroid-transforming enzymes.
      ,
      • Rižner T.L.
      • Penning T.M.
      Role of aldo–keto reductase family 1 (AKR1) enzymes in human steroid metabolism.
      ]. Our group has recently showed that higher AKR1C3 expression correlates with better overall survival in endometrioid EC [
      • Hojnik M.
      • et al.
      AKR1C3 is associated with better survival of patients with endometrial carcinomas.
      ]. Of note, both endometrioid and nonendometrioid tumor tissues lack CYP11B1 expression, suggesting that endometrial tumors most probably cannot metabolize classical androgens to 11-oxyandrogens. Nonetheless, active 11-oxyandrogens might form locally from 11-oxyandrogen precursors, such as 11β-OH-A4, present in relatively high systemic concentration. Indeed, genes coding for HSD11B2 and SRD5A enzymes express in endometrial tumors (Figure 3). Furthermore, the expression of SRD5A1 and SRD5A3 isoforms in EC tissue [
      • Sinreih M.
      • et al.
      Altered expression of genes involved in progesterone biosynthesis, metabolism and action in endometrial cancer.
      ,
      • Ito K.
      • et al.
      Expression of androgen receptor and 5α-reductases in the human normal endometrium and its disorders.
      ] suggests that DHT and 11-K-DHT can form locally.

      Microbiota as a source of bioactive androgens

      The microbiome, that is, a collection of genomes from all microorganisms that are part of the human body, is usually altered in cancer patients. In the case of EC, a multitude of factors, including menopausal status and BMI, were shown to influence the composition of the uterine microbiome, which in turn can contribute to EC development [
      • Walther-António M.R.
      • et al.
      Potential contribution of the uterine microbiome in the development of endometrial cancer.
      ,
      • Walsh D.M.
      • et al.
      Postmenopause as a key factor in the composition of the Endometrial Cancer Microbiome (ECbiome).
      ]. A study by Poore and collaborators examined whole-genome and whole-transcriptome data from treatment-naïve patients enrolled in TCGA study and identified that most major cancer types, including EC, have a unique microbial signature that enables the distinction of cancer-bearing from cancer-free individuals [
      • Poore G.D.
      • et al.
      Microbiome analyses of blood and tissues suggest cancer diagnostic approach.
      ].
      The altered microbiota can be a potential source of androgens and 11-oxyandrogens in EC patients. Indeed, the vast variety of unique enzymes enables the microbiota to convert steroid molecules to potent androgens, following deconjugation of the former from glucuronic acid or the sulfate group. For instance, a recent study focusing on possible androgen sources in castrate-resistant prostate cancer patients found out that some bacterial species of the intestinal microbial community can convert steroids, such as pregnenolone and 17α-OH-pregnenolone, to classical androgens, such as DHEA and T; some of them were enriched in patients with higher T levels [
      • Pernigoni N.
      • et al.
      Commensal bacteria promote endocrine resistance in prostate cancer through androgen biosynthesis.
      ]. Furthermore, the microbial community can use C21 glucocorticoids as an unconventional androgen source [
      • Devendran S.
      • et al.
      Identification and characterization of a 20β-HSDH from the anaerobic gut bacterium Butyricicoccus desmolans ATCC 43058.
      ]. For instance, a bacterial enzyme converting the glucocorticoid cortisol to 11β-OH-A4 has been described in bacterial species of the gut and urinary tract microbiota [
      • Devendran S.
      • et al.
      Identification and characterization of a 20β-HSDH from the anaerobic gut bacterium Butyricicoccus desmolans ATCC 43058.
      ,
      • Winter J.
      • et al.
      Mode of action of steroid desmolase and reductases synthesized by Clostridium "scindens" (formerly Clostridium strain 19).
      ,
      • Zimmermann M.
      • et al.
      Mapping human microbiome drug metabolism by gut bacteria and their genes.
      ].

      Biological significance of androgen signaling in endometrial tumors

      Androgens exert their biological function primarily via the AR. Several studies have assessed AR expression in different EC grades and types and compared it with that in endometrial hyperplasia, a precursor lesion of EC and healthy endometrial tissue [
      • Kamal A.M.
      • et al.
      Androgen receptors are acquired by healthy postmenopausal endometrial epithelium and their subsequent loss in endometrial cancer is associated with poor survival.
      ,
      • Tangen I.L.
      • et al.
      Androgen receptor as potential therapeutic target in metastatic endometrial cancer.
      ,
      • Gibson D.A.
      • et al.
      Evidence of androgen action in endometrial and ovarian cancers.
      ]. These studies showed that AR expression decreases with increasing endometrioid tumor grade, and it is lowest in tumors with nonendometrioid histology (Figure 4). While in primary endometrial tumors AR expression seems to correlate with lower grade and less aggressive disease, EC metastatic lesions with high AR:estrogen receptor (ER) ratio were correlated with poorer survival [
      • Tangen I.L.
      • et al.
      Androgen receptor as potential therapeutic target in metastatic endometrial cancer.
      ]. Altogether these data imply that AR signaling in EC is likely multifaceted and most probably differs throughout the tumor evolution.
      Figure 4
      Figure 4Androgen receptor (AR) signaling in endometrial cancer (EC).
      Upper panel (left): genomic AR signaling; in the presence of bioactive androgens, AR dissociates from chaperones and dimerizes. The ligand–receptor complex enters the nucleus and changes gene expression of target genes. Following palmitoylation, AR may associate on the membrane as part of a large signaling complex that includes other sex steroid hormones, such as estrogen receptor (ER) and progesterone receptor (PR), G protein-coupled receptors, as well as growth factor receptors, such as epithelial growth factor receptor (EGFR). Here, sex steroid receptors can transactivate growth factor receptors and cooperate in signal transduction with other sex steroid receptors. Upon ligand binding, a signal transduction occurs through physical interaction with G protein and kinases, such as PI3K, AKT, Src, which induce formation of second messengers. The evoked biological response is an integrated result of all signals in the cell at a particular time point. Lower panel (left): violin plot representing AR expression in different EC grades (median and interquartile ranges are represented). Lower panel (right): scatter plot representing protein levels of AR (x axis), ERα (y axis), and PR (color coded) expression in EC tumors. Note the positive association between AR, ERα, and to a certain extend PR expression in endometrial tumors. (Data extracted from [
      • Chang K.
      • et al.
      The Cancer Genome Atlas Pan-Cancer analysis project.
      ].) Created with BioRender (https://biorender.com/). Abbreviations: Hsp, heat shock protein; PI3K, phosphoinositide 3-kinase; RPPA, reverse phase protein array.
      Multiple lines of evidence indicate that androgens have antiproliferative effects on endometrial tumors. For instance, treatment with exogenous T was shown to reduce endometrial proliferation in both premenopausal [
      • Tuckerman E.M.
      • et al.
      Do androgens have a direct effect on endometrial function? An in vitro study.
      ,
      • Freis A.
      • et al.
      Effects of a hyperandrogenaemic state on the proliferation and decidualization potential in human endometrial stromal cells.
      ] and postmenopausal women [
      • Zang H.
      • et al.
      Effects of testosterone and estrogen treatment on the distribution of sex hormone receptors in the endometrium of postmenopausal women.
      ]. A4 was also shown to inhibit proliferation of endometrial cells in vitro [
      • Tuckerman E.M.
      • et al.
      Do androgens have a direct effect on endometrial function? An in vitro study.
      ]. The antiproliferative effect might be explained by androgens' counteracting effect on the proproliferative signaling of estrogens in the endometrium; this has already been confirmed in a well-differentiated endometrial adenocarcinoma cell line, Ishikawa [
      • Lovely L.P.
      • et al.
      Characterization of androgen receptors in a well-differentiated endometrial adenocarcinoma cell line (Ishikawa).
      ]. A more recent study focusing on breast cancer has provided a detailed mechanistic explanation of androgens' antitumor activity in ERα-positive breast cancer cells [
      • Hickey T.E.
      • et al.
      The androgen receptor is a tumor suppressor in estrogen receptor-positive breast cancer.
      ]. More specifically, the authors showed that AR can displace ER and other transcriptional coactivators from estrogen response elements, eventually leading to transcriptional downregulation of ER-regulated cell cycle genes and reduced proliferation of breast cancer cells.
      Androgens' protumoral effect is also plausible. For instance, T can be aromatized to estrogens in peripheral fatty depots [
      • Siiteri P.K.
      Adipose tissue as a source of hormones.
      ] and thus indirectly promotes tumor progression. In addition, these hormones can promote adipogenesis [
      • Carbone L.
      • et al.
      Synergistic effects of hyperandrogenemia and obesogenic Western-style diet on transcription and DNA methylation in visceral adipose tissue of nonhuman primates.
      ]; the adipose tissue then becomes an additional source of estrogens, as well as other steroid hormones, each exerting its own action on the endometrial tumor. Androgen signaling per se might be proproliferative as well. For instance, metastatic EC lesions with high AR:ERα ratio display an enrichment of cell cycle-associated gene sets, resulting in enhanced proliferation and consequently worse survival [
      • Tangen I.L.
      • et al.
      Androgen receptor as potential therapeutic target in metastatic endometrial cancer.
      ].
      A reasonable explanation of the seemingly contradictory role of androgens in EC might be provided by the complex integration of androgen signaling in the already altered cellular setup which is becoming even more and more compromised as the tumor evolves (Figure 1, Figure 4). Indeed, detailed studies on AR signaling in prostate and breast cancers have elucidated a crosstalk between androgen signaling and that of other steroid receptors, such as ER [
      • Rizza P.
      • et al.
      Estrogen receptor beta as a novel target of androgen receptor action in breast cancer cell lines.
      ], and nonsteroid receptors, such as growth factor receptors [
      • Naderi A.
      • Hughes-Davies L.
      A functionally significant cross-talk between androgen receptor and ErbB2 pathways in estrogen receptor negative breast cancer.
      ]. Furthermore, hetero-complexes between estrogen and androgen receptors, capable of responding to both ligands and thus integrating signals from estrogen and androgen hormones, were described in prostate and breast cancers as well [
      • Migliaccio A.
      • et al.
      Steroid-induced androgen receptor-oestradiol receptor beta-Src complex triggers prostate cancer cell proliferation.
      ]. Of note, the positive association between AR, ERα, and progesterone receptor (PR) expression levels presented in Figure 4 suggests that androgen signaling in EC might be only partially grasped if assessed independently from the other steroid hormone receptors (data extracted from TCGA's Pan-Cancer Atlas [
      • Chang K.
      • et al.
      The Cancer Genome Atlas Pan-Cancer analysis project.
      ]).
      To make matters more complicated, after post-translational modifications, such as palmitoylation, nuclear AR can also associate in a membrane signaling complex with other steroid and nonsteroid receptors; in these receptor-enriched membrane rafts, the activation of a particular receptor might influence the activity of other neighboring receptors as well (Figure 4) [
      • Levin E.R.
      • Hammes S.R.
      Nuclear receptors outside the nucleus: extranuclear signalling by steroid receptors.
      ]. Moreover, apart from signaling through AR, androgens can also activate alternative G protein-coupled receptors which then induce rapid signaling cascades and activate downstream pathways [
      • Pi M.
      • et al.
      GPRC6A mediates the non-genomic effects of steroids.
      ,
      • Pi M.
      • et al.
      Structural and functional evidence for testosterone activation of GPRC6A in peripheral tissues.
      ], such as the frequently altered PI-3-kinase/AKT pathway [
      • Baron S.
      • et al.
      Androgen receptor mediates non-genomic activation of phosphatidylinositol 3-OH kinase in androgen-sensitive epithelial cells.
      ]. Detailed studies of the molecular mechanisms of androgen signaling in EC are currently limited; however, these might be important in ensuring lasting effectiveness of even the most specifically designed molecular therapy.

      Concluding remarks

      The genomic hallmarks of EC involve frequent alterations in key cellular pathways that control cell cycle progression, cell growth, and apoptosis. While the exploitation of these alterations for tailoring molecular therapies holds great potential for tomorrow's EC management, the presence of adaptive redundant and parallel pathways, ultimately leading to the same outcome, that is, cell survival and proliferation, complicates these endeavors [
      • Nussinov R.
      • et al.
      Are parallel proliferation pathways redundant?.
      ,
      • Wilson M.R.
      • et al.
      ARID1A and PI3-kinase pathway mutations in the endometrium drive epithelial transdifferentiation and collective invasion.
      ]. Steroid hormones in the tumor milieu are adding additional complexity to the network of pathways governing the fate of tumor cells.
      Androgens have a multifaceted role in EC which differs throughout the tumor evolution (see Outstanding questions). This might be partly explained by the crosstalk and integration of androgen signaling pathways with that of other steroid and nonsteroid molecules.
      How important are androgens and 11-oxyandrogens in determining the fate of cells in endometrial tumors?
      Does the outcome of classical and nonclassical androgen signaling differ in EC?
      Is the ratio between classical androgens and 11-oxyandrogens important in EC?
      Do systemic 11-oxyandrogens have a diagnostic and/or prognostic value in EC?
      Can androgens and/or 11-oxyandrogens improve/impair the effectiveness of molecular targeted therapy for EC?

      Acknowledgments

      This work was supported by the Slovenian Research Agency (grant number J3-2535 to T.L.R.).

      Declaration of interests

      No interests are declared.

      References

        • Sung H.
        • et al.
        Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.
        CA Cancer J. Clin. 2021; 71: 209-249
        • Kocarnik J.M.
        • et al.
        Cancer incidence, mortality, years of life lost, years lived with disability, and disability-adjusted life years for 29 cancer groups from 2010 to 2019: a systematic analysis for the Global Burden of Disease Study 2019.
        JAMA Oncol. 2022; 8: 420-444
        • Board W.F.G.T.
        Female Genital Tumours: WHO Classification of Tumours.
        IARC, Lyon, France2020
        • Kandoth C.
        • et al.
        Integrated genomic characterization of endometrial carcinoma.
        Nature. 2013; 497: 67-73
        • Colombo N.
        • et al.
        ESMO-ESGO-ESTRO Consensus Conference on Endometrial Cancer: diagnosis, treatment and follow-up.
        Ann. Oncol. 2016; 27: 16-41
        • Concin N.
        • et al.
        ESGO/ESTRO/ESP guidelines for the management of patients with endometrial carcinoma.
        Int. J. Gynecol. Cancer. 2021; 31: 12
        • Zehir A.
        • et al.
        Mutational landscape of metastatic cancer revealed from prospective clinical sequencing of 10,000 patients.
        Nat. Med. 2017; 23: 703-713
        • Nguyen B.
        • et al.
        Genomic characterization of metastatic patterns from prospective clinical sequencing of 25,000 patients.
        Cell. 2022; 185: 563-575.e11
        • Sanchez-Vega F.
        • et al.
        Oncogenic signaling pathways in The Cancer Genome Atlas.
        Cell. 2018; 173: 321-337.e10
        • Dou Y.
        • et al.
        Proteogenomic characterization of endometrial carcinoma.
        Cell. 2020; 180: 729-748.e26
        • Soumerai T.E.
        • et al.
        Clinical utility of prospective molecular characterization in advanced endometrial cancer.
        Clin. Cancer Res. 2018; 24: 5939-5947
        • Bailey M.H.
        • et al.
        Comprehensive characterization of cancer driver genes and mutations.
        Cell. 2018; 173: 371-385.e18
        • Ott P.A.
        • et al.
        Safety and antitumor activity of pembrolizumab in advanced programmed death ligand 1–positive endometrial cancer: results from the KEYNOTE-028 study.
        J. Clin. Oncol. 2017; 35: 2535-2541
        • Oaknin A.
        • et al.
        Safety and antitumor activity of dostarlimab in patients with advanced or recurrent DNA mismatch repair deficient/microsatellite instability-high (dMMR/MSI-H) or proficient/stable (MMRp/MSS) endometrial cancer: interim results from GARNET—a phase I, single-arm study.
        J. Immunother. Cancer. 2022; 10e003777
        • Labrie F.
        • et al.
        DHEA and the intracrine formation of androgens and estrogens in peripheral target tissues: its role during aging.
        Steroids. 1998; 63: 322-328
        • Longcope C.
        Adrenal and gonadal androgen secretion in normal females.
        J. Clin. Endocrinol. Metab. 1986; 15: 213-228
        • Nanba A.T.
        • et al.
        11-oxygenated C19 steroids do not decline with age in women.
        J. Clin. Endocrinol. Metab. 2019; 104: 2615-2622
        • Caron P.
        • et al.
        A quantitative analysis of total and free 11-oxygenated androgens and its application to human serum and plasma specimens using liquid-chromatography tandem mass spectrometry.
        J. Chromatogr. A. 2021; 1650462228
        • Storbeck K.-H.
        • et al.
        11β-Hydroxydihydrotestosterone and 11-ketodihydrotestosterone, novel C19 steroids with androgenic activity: a putative role in castration resistant prostate cancer?.
        Mol. Cell. Endocrinol. 2013; 377: 135-146
        • Rege J.
        • et al.
        11-ketotestosterone is the dominant circulating bioactive androgen during normal and premature adrenarche.
        J. Clin. Endocrinol. Metab. 2018; 103: 4589-4598
        • Pretorius E.
        • et al.
        11-ketotestosterone and 11-ketodihydrotestosterone in castration resistant prostate cancer: potent androgens which can no longer be ignored.
        PLoS One. 2016; 11e0159867
        • Handelsman D.J.
        • et al.
        Bioactivity of 11 keto and hydroxy androgens in yeast and mammalian host cells.
        J. Steroid Biochem. Mol. Biol. 2022; 218106049
        • Brinkmann A.O.
        • et al.
        Structure and function of the androgen receptor.
        Urol. Res. 1989; 17: 87-93
        • Mertens H.J.M.M.
        • et al.
        Androgen, estrogen and progesterone receptor expression in the human uterus during the menstrual cycle.
        Eur. J. Obstet. Gynecol. Reprod. Biol. 2001; 98: 58-65
        • Marshall E.
        • et al.
        In silico analysis identifies a novel role for androgens in the regulation of human endometrial apoptosis.
        J. Clin. Endocrinol. Metab. 2011; 96: E1746-E1755
        • Gibson D.A.
        • et al.
        Regulation of androgen action during establishment of pregnancy.
        J. Mol. Endocrinol. 2016; 57: R35-R47
        • Kamal A.M.
        • et al.
        Androgen receptors are acquired by healthy postmenopausal endometrial epithelium and their subsequent loss in endometrial cancer is associated with poor survival.
        Br. J. Cancer. 2016; 114: 688-696
        • Siiteri P.K.
        Adipose tissue as a source of hormones.
        Am. J. Clin. Nutr. 1987; 45: 277-282
        • Lukanova A.
        • et al.
        Circulating levels of sex steroid hormones and risk of endometrial cancer in postmenopausal women.
        Int. J. Cancer. 2004; 108: 425-432
        • Michels K.A.
        • et al.
        Postmenopausal androgen metabolism and endometrial cancer risk in the Women's Health Initiative Observational Study.
        JNCI Cancer Spectr. 2019; 3: pkz029
        • Clendenen T.V.
        • et al.
        Premenopausal circulating androgens and risk of endometrial cancer: results of a prospective study.
        Horm. Cancer. 2016; 7: 178-187
        • Ruth K.S.
        • et al.
        Using human genetics to understand the disease impacts of testosterone in men and women.
        Nat. Med. 2020; 26: 252-258
        • Mullee A.
        • et al.
        Testosterone, sex hormone-binding globulin, insulin-like growth factor-1 and endometrial cancer risk: observational and Mendelian randomization analyses.
        Br. J. Cancer. 2021; 125: 1308-1317
        • Danforth K.N.
        • et al.
        The association of plasma androgen levels with breast, ovarian and endometrial cancer risk factors among postmenopausal women.
        Int. J. Cancer. 2010; 126: 199-207
        • Allen N.E.
        • et al.
        Endogenous sex hormones and endometrial cancer risk in women in the European Prospective Investigation into Cancer and Nutrition (EPIC).
        Endocr. Relat. Cancer. 2008; 15: 485
        • O’Mara T.A.
        • et al.
        Identification of nine new susceptibility loci for endometrial cancer.
        Nat. Commun. 2018; 9: 3166
        • Bhaskaran K.
        • et al.
        Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5.24 million UK adults.
        Lancet. 2014; 384: 755-765
        • Park I.S.
        • et al.
        Risk of female-specific cancers according to obesity and menopausal status in 2.7 million Korean women: similar trends between Korean and Western women.
        Lancet Reg. Health West Pac. 2021; 11100146
        • Yin W.
        • et al.
        Association between polycystic ovary syndrome and cancer risk.
        JAMA Oncol. 2019; 5: 106-107
        • Taylor A.
        • et al.
        11-oxyandrogen concentrations in adolescents with polycystic ovary syndrome (PCOS).
        J. Endocr. Soc. 2021; 6: bvac037
        • Miller W.L.
        • Auchus R.J.
        The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders.
        Endocr. Rev. 2011; 32: 81-151
        • Shimizu K.
        • et al.
        The transformation of 20α-hydroxycholesterol to isocaproic acid and C21 steroids.
        J. Biol. Chem. 1961; 236: 695-699
        • Zuber Mauricio X.
        • et al.
        Expression of bovine 17α-hydroxylase cytochrome P-450 cDNA in nonsteroidogenic (COS 1) cells.
        Science. 1986; 234: 1258-1261
        • Auchus R.J.
        • et al.
        Cytochrome b5 augments the 17,20-lyase activity of human P450c17 without direct electron transfer.
        J. Biol. Chem. 1998; 273: 3158-3165
        • Labrie F.
        • et al.
        Structure, function and tissue-specific gene expression of 3β-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase enzymes in classical and peripheral intracrine steroidogenic tissues.
        J. Steroid Biochem. Mol. Biol. 1992; 43: 805-826
        • Nakamura Y.
        • et al.
        Type 5 17β-hydroxysteroid dehydrogenase (AKR1C3) contributes to testosterone production in the adrenal reticularis.
        J. Clin. Endocrinol. Metab. 2009; 94: 2192-2198
        • Mornet E.
        • et al.
        Characterization of two genes encoding human steroid 11β-hydroxylase (P-45011β)*.
        J. Biol. Chem. 1989; 264: 20961-20967
        • Blouin K.
        • et al.
        Pathways of adipose tissue androgen metabolism in women: depot differences and modulation by adipogenesis.
        Am. J. Physiol. Endocrinol. Metab. 2009; 296: E244-E255
        • Rižner T.L.
        • et al.
        The importance of steroid uptake and intracrine action in endometrial and ovarian cancers.
        Front. Pharmacol. 2017; 8: 346
        • Okamoto N.
        • et al.
        A membrane transporter is required for steroid hormone uptake in Drosophila.
        Dev. Cell. 2018; 47: 294-305.e7
        • Sissung T.M.
        • et al.
        Differential expression of OATP1B3 mediates unconjugated testosterone influx.
        Mol. Cancer Res. 2017; 15: 1096-1105
        • Hammes A.
        • et al.
        Role of endocytosis in cellular uptake of sex steroids.
        Cell. 2005; 122: 751-762
        • Han Y.
        • et al.
        Crystal structure of steroid reductase SRD5A reveals conserved steroid reduction mechanism.
        Nat. Commun. 2021; 12: 449
        • Barnard M.
        • et al.
        11-Oxygenated androgen precursors are the preferred substrates for aldo-keto reductase 1C3 (AKR1C3): implications for castration resistant prostate cancer.
        J. Steroid Biochem. Mol. Biol. 2018; 183: 192-201
        • Sinreih M.
        • et al.
        Altered expression of genes involved in progesterone biosynthesis, metabolism and action in endometrial cancer.
        Chem. Biol. Interact. 2013; 202: 210-217
        • Hojnik M.
        • et al.
        AKR1C3 is associated with better survival of patients with endometrial carcinomas.
        J. Clin. Med. 2020; 9: 4105
        • Ito K.
        • et al.
        Expression of androgen receptor and 5α-reductases in the human normal endometrium and its disorders.
        Int. J. Cancer. 2002; 99: 652-657
        • Rižner T.L.
        • et al.
        AKR1C1 and AKR1C3 may determine progesterone and estrogen ratios in endometrial cancer.
        Mol. Cell. Endocrinol. 2006; 248: 126-135
        • Šmuc T.
        • Rižner T.L.
        Aberrant pre-receptor regulation of estrogen and progesterone action in endometrial cancer.
        Mol. Cell. Endocrinol. 2009; 301: 74-82
        • Hevir-Kene N.
        • Rižner T.L.
        The endometrial cancer cell lines Ishikawa and HEC-1A, and the control cell line HIEEC, differ in expression of estrogen biosynthetic and metabolic genes, and in androstenedione and estrone-sulfate metabolism.
        Chem. Biol. Interact. 2015; 234: 309-319
        • Chang K.
        • et al.
        The Cancer Genome Atlas Pan-Cancer analysis project.
        Nat. Genet. 2013; 45: 1113-1120
        • Cerami E.
        • et al.
        The cBio cancer genomics portal: an open platform for exploring multidimensional cancer genomics data.
        Cancer Discov. 2012; 2: 401-404
        • Gao J.
        • et al.
        Integrative analysis of complex cancer genomics and clinical profiles using the cBioPortal.
        Sci. Signal. 2013; 6: pl1
        • Pavlič R.
        • et al.
        Altered profile of E1-S transporters in endometrial cancer: lower protein levels of ABCG2 and OSTβ and up-regulation of SLCO1B3 expression.
        Int. J. Mol. Sci. 2021; 22: 3819
        • Penning T.M.
        • et al.
        Structural and functional biology of aldo-keto reductase steroid-transforming enzymes.
        Endocr. Rev. 2019; 40: 447-475
        • Rižner T.L.
        • Penning T.M.
        Role of aldo–keto reductase family 1 (AKR1) enzymes in human steroid metabolism.
        Steroids. 2014; 79: 49-63
        • Walther-António M.R.
        • et al.
        Potential contribution of the uterine microbiome in the development of endometrial cancer.
        Genome Med. 2016; 8: 122
        • Walsh D.M.
        • et al.
        Postmenopause as a key factor in the composition of the Endometrial Cancer Microbiome (ECbiome).
        Sci. Rep. 2019; 9: 19213
        • Poore G.D.
        • et al.
        Microbiome analyses of blood and tissues suggest cancer diagnostic approach.
        Nature. 2020; 579: 567-574
        • Pernigoni N.
        • et al.
        Commensal bacteria promote endocrine resistance in prostate cancer through androgen biosynthesis.
        Science. 2021; 374: 216-224
        • Devendran S.
        • et al.
        Identification and characterization of a 20β-HSDH from the anaerobic gut bacterium Butyricicoccus desmolans ATCC 43058.
        J. Lipid Res. 2017; 58: 916-925
        • Winter J.
        • et al.
        Mode of action of steroid desmolase and reductases synthesized by Clostridium "scindens" (formerly Clostridium strain 19).
        J. Lipid Res. 1984; 25: 1124-1131
        • Zimmermann M.
        • et al.
        Mapping human microbiome drug metabolism by gut bacteria and their genes.
        Nature. 2019; 570: 462-467
        • Tangen I.L.
        • et al.
        Androgen receptor as potential therapeutic target in metastatic endometrial cancer.
        Oncotarget. 2016; 7: 49289-49298
        • Gibson D.A.
        • et al.
        Evidence of androgen action in endometrial and ovarian cancers.
        Endocr. Relat. Cancer. 2014; 21: T203-T218
        • Tuckerman E.M.
        • et al.
        Do androgens have a direct effect on endometrial function? An in vitro study.
        Fertil. Steril. 2000; 74: 771-779
        • Freis A.
        • et al.
        Effects of a hyperandrogenaemic state on the proliferation and decidualization potential in human endometrial stromal cells.
        Arch. Gynecol. Obstet. 2017; 295: 1005-1013
        • Zang H.
        • et al.
        Effects of testosterone and estrogen treatment on the distribution of sex hormone receptors in the endometrium of postmenopausal women.
        Menopause. 2008; 15: 233-239
        • Lovely L.P.
        • et al.
        Characterization of androgen receptors in a well-differentiated endometrial adenocarcinoma cell line (Ishikawa).
        J. Steroid Biochem. Mol. Biol. 2000; 74: 235-241
        • Hickey T.E.
        • et al.
        The androgen receptor is a tumor suppressor in estrogen receptor-positive breast cancer.
        Nat. Med. 2021; 27: 310-320
        • Carbone L.
        • et al.
        Synergistic effects of hyperandrogenemia and obesogenic Western-style diet on transcription and DNA methylation in visceral adipose tissue of nonhuman primates.
        Sci. Rep. 2019; 9: 19232
        • Rizza P.
        • et al.
        Estrogen receptor beta as a novel target of androgen receptor action in breast cancer cell lines.
        Breast Cancer Res. 2014; 16: R21
        • Naderi A.
        • Hughes-Davies L.
        A functionally significant cross-talk between androgen receptor and ErbB2 pathways in estrogen receptor negative breast cancer.
        Neoplasia. 2008; 10: 542-548
        • Migliaccio A.
        • et al.
        Steroid-induced androgen receptor-oestradiol receptor beta-Src complex triggers prostate cancer cell proliferation.
        EMBO J. 2000; 19: 5406-5417
        • Levin E.R.
        • Hammes S.R.
        Nuclear receptors outside the nucleus: extranuclear signalling by steroid receptors.
        Nat. Rev. Mol. Cell Biol. 2016; 17: 783-797
        • Pi M.
        • et al.
        GPRC6A mediates the non-genomic effects of steroids.
        J. Biol. Chem. 2010; 285: 39953-39964
        • Pi M.
        • et al.
        Structural and functional evidence for testosterone activation of GPRC6A in peripheral tissues.
        Mol. Endocrinol. 2015; 29: 1759-1773
        • Baron S.
        • et al.
        Androgen receptor mediates non-genomic activation of phosphatidylinositol 3-OH kinase in androgen-sensitive epithelial cells.
        J. Biol. Chem. 2004; 279: 14579-14586
        • Nussinov R.
        • et al.
        Are parallel proliferation pathways redundant?.
        Trends Biochem. Sci. 2020; 45: 554-563
        • Wilson M.R.
        • et al.
        ARID1A and PI3-kinase pathway mutations in the endometrium drive epithelial transdifferentiation and collective invasion.
        Nat. Commun. 2019; 10: 3554

      Glossary

      Disability-adjusted life years (DALYs) index
      sum of years lived with a disability and years lost due to premature mortality caused by a particular disease.
      Fraction of genome altered (FGA)
      the percentage of the genome that has been affected by copy number gains or losses.
      Molecular targeted therapy
      therapy designed to modulate the function of a protein or other cellular components linked to a particular disease.
      Phosphatidylinositol 3 (PI-3)-kinase/AKT pathway
      a key regulatory hub for cell growth, survival, and metabolism.
      Steroidogenesis
      the process of steroid synthesis.
      Tumor mutational burden (TMB)
      the number of somatic mutations per million bases.