Minireview: Androgen metabolism in castration-resistant prostate cancer

R-loop resolution by ARIP4 helicase promotes androgen-mediated transcription induction

Pausing of RNA polymerase II (Pol II) at transcription start sites (TSSs) primes target genes for productive elongation. Coincidentally, DNA double-strand breaks (DSBs) enrich at highly transcribed and Pol II-paused genes, although their interplay remains undefined. Using androgen receptor (AR) signaling as a model, we have uncovered AR-interacting protein 4 (ARIP4) helicase as a driver of androgen-dependent transcription induction. Chromatin immunoprecipitation sequencing analysis revealed that ARIP4 preferentially co-occupies TSSs with paused Pol II. Moreover, we found that ARIP4 complexes with topoisomerase II beta and mediates transient DSB formation upon hormone stimulation. Accordingly, ARIP4 deficiency compromised release of paused Pol II and resulted in R-loop accumulation at a panel of highly transcribed AR target genes. Last, we showed that ARIP4 binds and unwinds R-loops in vitro and that its expression positively correlates with prostate cancer progression. We propose that androgen stimulation triggers ARIP4-mediated unwinding of R-loops at TSSs, enforcing Pol II pause release to effectively drive an androgen-dependent expression program.

Unveiling hormone-stimulated gene mechanisms in prostate cancer: A prognostic model, immune infiltration analysis, and drug sensitivity study

Hormones promote the progression of prostate cancer (PRCA) through the activation of a complex regulatory network. Inhibition of hormones or modulation of specific network nodes alone is insufficient to suppress the entire oncogenic network. Therefore, it is imperative to elucidate the mechanisms underlying the occurrence and development of PRCA in order to identify reliable diagnostic markers and therapeutic targets. To this end, we used publicly available data to analyze the potential mechanisms of hormone-stimulated genes in PRCA, construct a prognostic model, and assess immune infiltration and drug sensitivity. The single-cell RNA-sequencing data of PRCA were subjected to dimensionality reduction clustering and annotation, and the cells were categorized into two groups based on hormone stimulus-related scores. The differentially expressed genes between the two groups were screened and incorporated into the least absolute shrinkage and selection operator machine learning algorithm, and a prognostic model comprising six genes (ZNF862, YIF1A, USP22, TAF7, SRSF3, and SPARC) was constructed. The robustness of the model was validation through multiple methods. Immune infiltration scores in the two risk groups were calculated using three different algorithms. In addition, the relationship between the model genes and immune cell infiltration, and that between risk score and immune cell infiltration were analyzed. Drug sensitivity analysis was performed for the model genes and risk score using public databases to identify potential candidate drugs. Our findings provide novel insights into the mechanisms of hormone-stimulated genes in PRCA progression, prognosis, and drug screening.

Chronic hypoxia stabilizes 3βHSD1 via autophagy suppression

Progression of prostate cancer depends on androgen receptor, which is usually activated by androgens. Therefore, a mainstay treatment is androgen deprivation therapy. Unfortunately, despite initial treatment response, resistance nearly always develops, and disease progresses to castration-resistant prostate cancer (CRPC), which remains driven by non-gonadal androgens synthesized in prostate cancer tissues. 3β-Hydroxysteroid dehydrogenase/Δ5-->4 isomerase 1 (3βHSD1) catalyzes the rate-limiting step in androgen synthesis. However, how 3βHSD1, especially the "adrenal-permissive" 3βHSD1(367T) that permits tumor synthesis of androgen from dehydroepiandrosterone (DHEA), is regulated at the protein level is not well understood. Here, we investigate how hypoxia regulates 3βHSD1(367T) protein levels. Our results show that, in vitro, hypoxia stabilizes 3βHSD1 protein by suppressing autophagy. Autophagy inhibition promotes 3βHSD1-dependent tumor progression. Hypoxia represses transcription of autophagy-related (ATG) genes by decreasing histone acetylation. Inhibiting deacetylase (HDAC) restores ATG gene transcription under hypoxia. Therefore, HDAC inhibition may be a therapeutic target for hypoxic tumor cells.

Intratumoral androgen biosynthesis associated with 3β-hydroxysteroid dehydrogenase 1 promotes resistance to radiotherapy in prostate cancer

Half of all men with advanced prostate cancer (PCa) inherit at least 1 copy of an adrenal-permissive HSD3B1 (1245C) allele, which increases levels of 3β-hydroxysteroid dehydrogenase 1 (3βHSD1) and promotes intracellular androgen biosynthesis. Germline inheritance of the adrenally permissive allele confers worse outcomes in men with advanced PCa. We investigated whether HSD3B1 (1245C) drives resistance to combined androgen deprivation and radiotherapy. Adrenally permissive 3βHSD1 enhanced resistance to radiotherapy in PCa cell lines and xenograft models engineered to mimic the human adrenal/gonadal axis during androgen deprivation. The allele-specific effects on radiosensitivity were dependent on availability of DHEA, the substrate for 3βHSD1. In lines expressing the HSD3B1 (1245C) allele, enhanced expression of DNA damage response (DDR) genes and more rapid DNA double-strand break (DSB) resolution were observed. A correlation between androgen receptor (AR) expression and increased DDR gene expression was confirmed in 680 radical prostatectomy specimens. Treatment with the nonsteroidal antiandrogen enzalutamide reversed the resistant phenotype of HSD3B1 (1245C) PCa in vitro and in vivo. In conclusion, 3βHSD1 promotes prostate cancer resistance to combined androgen deprivation and radiotherapy by upregulating DNA DSB repair. This work supports prospective validation of early combined androgen blockade for high-risk men harboring the HSD3B1 (1245C) allele.

Lineage plasticity and treatment resistance in prostate cancer: the intersection of genetics, epigenetics, and evolution

Androgen deprivation therapy is a cornerstone of treatment for advanced prostate cancer, and the development of castrate-resistant prostate cancer (CRPC) is the primary cause of prostate cancer-related mortality. While CRPC typically develops through a gain in androgen receptor (AR) signaling, a subset of CRPC will lose reliance on the AR. This process involves genetic, epigenetic, and hormonal changes that promote cellular plasticity, leading to AR-indifferent disease, with neuroendocrine prostate cancer (NEPC) being the quintessential example. NEPC is enriched following treatment with second-generation anti-androgens and exhibits resistance to endocrine therapy. Loss of RB1, TP53, and PTEN expression and MYCN and AURKA amplification appear to be key drivers for NEPC differentiation. Epigenetic modifications also play an important role in the transition to a neuroendocrine phenotype. DNA methylation of specific gene promoters can regulate lineage commitment and differentiation. Histone methylation can suppress AR expression and promote neuroendocrine-specific gene expression. Emerging data suggest that EZH2 is a key regulator of this epigenetic rewiring. Several mechanisms drive AR-dependent castration resistance, notably AR splice variant expression, expression of the adrenal-permissive 3βHSD1 allele, and glucocorticoid receptor expression. Aberrant epigenetic regulation also promotes radioresistance by altering the expression of DNA repair- and cell cycle-related genes. Novel therapies are currently being developed to target these diverse genetic, epigenetic, and hormonal mechanisms promoting lineage plasticity-driven NEPC.

Serum Androgen Metabolites Correlate with Clinical Variables in African and European American Men with Localized, Therapy Naïve Prostate Cancer

Dihydrotestosterone (DHT) and testosterone (T), which mediate androgen receptor nuclear translocation and target gene transcription, are crucial androgens and essential molecular triggers required for the proliferation and survival of prostate cancer cells. Therefore, androgen metabolism is commonly targeted in the treatment of prostate cancer. Using a high-pressure liquid chromatographic assay with tandem mass spectral detection, we determined the serum levels of metabolites produced during DHT/T biosynthesis in African American (AA) and European American (EA) men with localized, therapy naïve prostate cancer. Serum progesterone and related metabolites were significantly lower in AA men than in EA men, and these differences were associated with rapid disease progression. Multivariate analysis revealed significant differences between a subset of intermediate androgen metabolites between AA and EA men and between men with <=3 + 4 and >=4 + 3 Gleason score disease. AA men have a significantly higher frequency of single nucleotide polymorphisms in CYP11B1 and CYP11B2, enzymes that regulate corticosterone-aldosterone conversion. Finally, higher levels of T and pregnenolone were associated with a lower risk of progression-free survival only in AA men. This work provides new insight into androgen metabolism and racial disparities in prostate cancer by presenting evidence of dysregulated androgen biosynthesis in therapy naïve disease that correlates with clinical variables.

BMX controls 3βHSD1 and sex steroid biosynthesis in cancer

Prostate cancer is highly dependent on androgens and the androgen receptor (AR). Hormonal therapies inhibit gonadal testosterone production, block extragonadal androgen biosynthesis, or directly antagonize AR. Resistance to medical castration occurs as castration-resistant prostate cancer (CRPC) and is driven by reactivation of the androgen-AR axis. 3β-hydroxysteroid dehydrogenase-1 (3βHSD1) serves as the rate-limiting step for potent androgen synthesis from extragonadal precursors, thereby stimulating CRPC. Genetic evidence in men demonstrates the role of 3βHSD1 in driving CRPC. In postmenopausal women, 3βHSD1 is required for synthesis of aromatase substrates and plays an essential role in breast cancer. Therefore, 3βHSD1 lies at a critical junction for the synthesis of androgens and estrogens, and this metabolic flux is regulated through germline-inherited mechanisms. We show that phosphorylation of tyrosine 344 (Y344) occurs and is required for 3βHSD1 cellular activity and generation of Δ4, 3-keto-substrates of 5α-reductase and aromatase, including in patient tissues. BMX directly interacts with 3βHSD1 and is necessary for enzyme phosphorylation and androgen biosynthesis. In vivo blockade of 3βHSD1 Y344 phosphorylation inhibits CRPC. These findings identify what we believe to be new hormonal therapy pharmacologic vulnerabilities for sex-steroid dependent cancers.

Adrenal Steroids and Resistance to Hormonal Blockade of Prostate and Breast Cancer

Prostate cancer and breast cancer are sex-steroid-dependent diseases that are driven in major part by gonadal sex steroids. Testosterone (T) is converted to 5α-dihydrotestosterone, both of which stimulate the androgen receptor (AR) and prostate cancer progression. Estradiol is the major stimulus for estrogen receptor-α (ERα) and proliferation of ERα-expressing breast cancer. However, the human adrenal provides an alternative source for sex steroids. A number of different androgens are produced by the adrenals, the most abundant of which is dehydroepiandrosterone (DHEA) and DHEA sulfate. These precursor steroids are subject to metabolism by peripherally expressed enzymes that are responsible for the synthesis of potent androgens and estrogens. In the case of prostate cancer, the regulation of one of these enzymatic steps occurs at least in part by way of a germline-encoded missense in 3β-hydroxysteroid dehydrogenase-1 (3βHSD1), which regulates potent androgen biosynthesis and clinical outcomes in men with advanced prostate cancer treated with gonadal T deprivation. The sex steroids that drive prostate cancer and breast cancer require a common set of enzymes for their generation. However, the pathways diverge once 3-keto, Δ4-androgens are generated and these steroids are either turned into potent androgens by steroid-5α-reductase, or into estrogens by aromatase. Alternative steroid receptors have also emerged as disease- and treatment-resistance modifiers, including a role for AR in breast cancer and glucocorticoid receptor both in breast and prostate cancer. In this review, we integrate the commonalities of adrenal steroid physiology that regulate both prostate and breast cancer while recognizing the clear distinctions between these diseases.

Association Between Adrenal-Restrictive HSD3B1 Inheritance and Hormone-Independent Subtypes of Endometrial and Breast Cancer

BACKGROUND

The germline variant rs1047303 (HSD3B1[1245A/C]), restricting or enabling production of potent androgens and estrogens from adrenal precursors, affects outcomes of castration-resistant prostate cancer and is associated with estrogen receptor positivity in postmenopausal breast cancer. Like breast cancer, endometrial cancer is another malignancy with hormone-dependent and hormone-independent subtypes. We hypothesized that adrenal-restrictive HSD3B1 genotype would associate with hormone-independent cancer subtypes.

METHODS

We employed a previously described classification of tumors in The Cancer Genome Atlas into genomic clusters. We determined HSD3B1 genotype frequencies by endometrial cancer genomic cluster and calculated the odds per adrenal-restrictive A allele for the largely hormone-independent copy-number (CN) high subtype vs other subtypes. An equivalent analysis was performed for the genomically similar, hormone-independent basal breast cancer subtype. Last, we performed survival analyses for UK Biobank participants with endometrial cancer by HSD3B1 genotype. All statistical tests were 2-sided.

RESULTS

The adrenal-restrictive HSD3B1(1245A) allele was associated with the CN-high endometrial cancer subtype (odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.14 to 2.32; P = .007). Similarly, HSD3B1(1245A) was associated with the basal breast cancer subtype (OR = 1.54, 95% CI = 1.13 to 2.08; P = .006). In the UK Biobank, endometrial cancer patients homozygous for HSD3B1(1245A) had worse overall (hazard ratio [HR] = 1.39, 95% CI = 1.16 to 1.68; P < .001) and cancer-specific (HR = 1.39, 95% CI = 1.14 to 1.70; P = .001) survival, consistent with the A allele being enriched in the more aggressive CN-high subtype.

CONCLUSIONS

These findings suggest roles for adrenal-restrictive vs adrenal-permissive steroidogenesis, by way of rs1047303 genotype, in the development of and/or outcomes from at least 3 commonly hormone-associated types of cancer: prostate, breast, and endometrial.

Two calix[4]pyrroles as potential therapeutics for castration-resistant prostate cancer

Macrocyclic compounds meso-(p-acetamidophenyl)-calix[4]pyrrole and meso-(m-acetamidophenyl)-calix[4]pyrrole have previously been reported to exhibit cytotoxic properties towards lung cancer cells. Here, we report pre-clinical in vitro and in vivo studies showing that these calixpyrrole derivatives can inhibit cell growth in both PC3 and DU145 prostatic cancer cell lines. We explored the impact of these compounds on programmed cell death, as well as their ability to inhibit cellular invasion. In this study we have demonstrated the safety of these macrocyclic compounds by cytotoxicity tests on ex-vivo human peripheral blood mononuclear cells (PBMCs), and by in vivo subcutaneous administration. Preliminary in vivo tests demonstrated no hepato-, no nephro- and no genotoxicity in Balb/c mice compared to controls treated with cisplatin. These findings suggest these calixpyrroles might be novel therapeutic tools for the treatment of prostate cancer and of particular interest for the treatment of androgen-independent castration-resistant prostate cancer.

The functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination

Ubiquitination of substrates usually have two fates: one is degraded by 26S proteasome, and the other is non-degradative ubiquitination modification which is associated with cell cycle regulation, chromosome inactivation, protein transportation, tumorigenesis, achondroplasia, and neurological diseases. Cullin3 (CUL3), a scaffold protein, binding with the Bric-a-Brac-Tramtrack-Broad-complex (BTB) domain of substrates recognition adaptor and RING-finger protein 1 (RBX1) form ubiquitin ligases (E3). Based on the current researches, this review has summarized the functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination.

Hypoxia-Reoxygenation Couples 3βHSD1 Enzyme and Cofactor Upregulation to Facilitate Androgen Biosynthesis and Hormone Therapy Resistance in Prostate Cancer

Androgen deprivation therapy suppresses tumor androgen receptor (AR) signaling by depleting circulating testosterone and is a mainstay treatment for advanced prostate cancer. Despite initial treatment response, castration-resistant prostate cancer nearly always develops and remains driven primarily by the androgen axis. Here we investigated how changes in oxygenation affect androgen synthesis. In prostate cancer cells, chronic hypoxia coupled to reoxygenation resulted in efficient metabolism of androgen precursors to produce androgens and activate AR. Hypoxia induced 3βHSD1, the rate-limiting androgen synthesis regulator, and reoxygenation replenished necessary cofactors, suggesting that hypoxia and reoxygenation both facilitate potent androgen synthesis. The EGLN1/VHL/HIF2α pathway induced 3βHSD1 expression through direct binding of HIF2α to the 5' regulatory region of HSD3B1 to promote transcription. Overexpression of HIF2α facilitated prostate cancer progression, which largely depended on 3βHSD1. Inhibition of HIF2α with the small-molecule PT2399 prevented prostate cancer cell proliferation. These results thus identify HIF2α as a regulator of androgen synthesis and potential therapeutic target in prostate cancer.

SIGNIFICANCE

Hypoxia followed by reoxygenation in prostate cancer drives androgen deprivation therapy resistance via increasing the rate-limiting enzyme and cofactors for androgen synthesis, revealing HIF2α as a therapeutic target to subvert resistance.

Multi-omics & pathway analysis identify potential roles for tumor N-acetyl aspartate accumulation in murine models of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is incurable and remains a significant worldwide challenge (Oakes and Papa, 2015). Matched untargeted multi-level omic datasets may reveal biological changes driving CRPC, identifying novel biomarkers and/or therapeutic targets. Untargeted RNA sequencing, proteomics, and metabolomics were performed on xenografts derived from three independent sets of hormone naive and matched CRPC human cell line models of local, lymph node, and bone metastasis grown as murine orthografts. Collectively, we tested the feasibility of muti-omics analysis on models of CRPC in revealing pathways of interest for future validation investigation. Untargeted metabolomics revealed NAA and NAAG commonly accumulating in CRPC across three independent models and proteomics showed upregulation of related enzymes, namely N-acetylated alpha-linked acidic dipeptidases (FOLH1/NAALADL2). Based on pathway analysis integrating multiple omic levels, we hypothesize that increased NAA in CRPC may be due to upregulation of NAAG hydrolysis via NAALADLases providing a pool of acetyl Co-A for upregulated sphingolipid metabolism and a pool of glutamate and aspartate for nucleotide synthesis during tumor growth.

Altered glucuronidation deregulates androgen dependent response profiles and signifies castration resistance in prostate cancer

Glucuronidation controls androgen levels in the prostate and the dysregulation of enzymes in this pathway is associated with castration resistant prostate cancer. UDP-glucose dehydrogenase (UGDH) produces UDP-glucuronate, the essential precursor for glucuronidation, and its expression is elevated in prostate cancer. We compared protein and metabolite levels relevant to the glucuronidation pathway in five prostate cancer patient-derived xenograft models paired with their isogenic counterparts that were selected in vivo for castration resistant (CR) recurrence. All pairs showed changes in UGDH and associated enzymes and metabolites that were consistent with those we found in an isogenic androgen dependent (AD) and CR LNCaP prostate cancer model. Ectopic overexpression of UGDH in LNCaP AD cells blunted androgen-dependent gene expression, increased proteoglycan synthesis, significantly increased cell growth compared to controls, and eliminated dose responsive growth suppression with enzalutamide treatment. In contrast, the knockdown of UGDH diminished proteoglycans, suppressed androgen dependent growth irrespective of androgens, and restored androgen sensitivity in CR cells. Importantly, the knockdown of UGDH in both LNCaP AD and CR cells dramatically sensitized these cells to enzalutamide. These results support a role for UGDH in androgen responsiveness and a target for therapeutic strategies in advanced prostate cancer.

Macrophage-derived cholesterol contributes to therapeutic resistance in prostate cancer

Castration-resistant prostate cancer (CRPC) is a lethal stage of disease in which androgen receptor (AR) signaling is persistent despite androgen deprivation therapy (ADT). Most studies have focused on investigating cell-autonomous alterations in CRPC, while the contributions of the tumor microenvironment are less well understood. Here we sought to determine the role of tumor-associated macrophages in CRPC, based upon their role in cancer progression and therapeutic resistance. In a syngeneic model that reflected the mutational landscape of CRPC, macrophage depletion resulted in a reduced transcriptional signature for steroid and bile acid synthesis, indicating potential perturbation of cholesterol metabolism. As cholesterol is the precursor of the five major types of steroid hormones, we hypothesized that macrophages were regulating androgen biosynthesis within the prostate tumor microenvironment. Macrophage depletion reduced androgen levels within prostate tumors and restricted androgen receptor (AR) nuclear localization in vitro and in vivo. Macrophages were also cholesterol-rich and were able to transfer cholesterol to tumor cells in vitro. AR nuclear translocation was inhibited by activation of Liver X Receptor (LXR)-β, the master regulator of cholesterol homeostasis. Consistent with these data, macrophage depletion extended survival during ADT and the presence of macrophages correlated with therapeutic resistance in patient-derived explants. Taken together, these findings support the therapeutic targeting of macrophages in CRPC.

Orphan nuclear receptors as regulators of intratumoral androgen biosynthesis in castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) almost invariably occurs after androgen-deprivation therapy (ADT) for the advanced metastatic disease. It is generally believed that among multiple mechanisms and signaling pathways, CRPC is significantly driven by the reactivation of androgen receptor (AR) signaling in ADT-treated patients with castrate levels of androgen, partially at least mediated by the androgen biosynthesis within the tumor, also known as intratumoral or intraprostatic androgen biosynthesis. Steroidogenic enzymes, such as CYP11A1, CYP17A1, HSD3B1, AKR1C3 and SRD5A, are essential to catalyze the conversion of the initial substrate cholesterol into potent androgens that confers the CRPC progression. Accumulating evidences indicate that many steroidogenic enzymes are upregulated in the progression setting; however, little is known about the dysregulation of these enzymes in CRPC. Orphan nuclear receptors (ONRs) are members of the nuclear receptor superfamily, of which endogenous physiological ligands are unknown and which are constitutively active independent of any physiological ligands. Studies have validated that besides AR, ONRs could be the potential therapeutic targets for prostate cancer, particularly the lethal CRPC progression. Early studies reveal that ONRs play crucial roles in the transcriptional regulation of steroidogenic enzyme genes. Notably, we and others show that three distinct ONRs, including liver receptor homolog-1 (LRH-1, NR5A2), steroidogenic factor 1 (SF-1, AD4BP, NR5A1) and estrogen-related receptor α (ERRα, NR3B1), can contribute to the CRPC progression by promotion of the intratumoral androgen synthesis via their direct transcriptional regulation on multiple steroidogenic enzymes. This review presents an overview of the current understanding on the intratumoral androgen biosynthesis in CRPC, with a special focus on the emerging roles of ONRs in this process.

HSD3B1 variant and androgen-deprivation therapy outcome in prostate cancer

OBJECTIVE

Rate-limiting enzyme 3b-hydroxysteroid dehydrogenase type 1 (3βHSD1) encoded by HSD3B1 catalyzes the transition of dehydroepiandrosterone (DHEA) to dihydrotestosterone (DHT). The HSD3B1 (1245C) variant renders 3bHSD1 of resistant to ubiquitination and degradation, leading to a large amount of protein accumulation in the cell. Multiple clinical studies have shown that this mutation was correlated with resistance to androgen-deprivation therapy in prostate cancer. However, the results were not consistent depending on different treatment strategy and in some researches, the number of observed cases was relatively small.

METHODS

To determine the effects of HSD3B1 (1245C) variant on resistance to androgen-deprivation therapy in prostate cancer, we performed a meta-analysis of the available literature. Electronic database searches identified appropriately designed studies that detected HSD3B1 in prostate cancer. We conducted a systematic search of studies in the following databases: PubMed, and EMBASE published until August 10, 2020 using the following search terms: (HSD3B1 AND ((((prostate cancer) OR prostatic neoplasm) OR prostatic carcinoma) OR prostatic cancer).

RESULTS

Eight researches were included in this research. The result validated that the HSD3B1 (1245C) variant allele was associated with a shorter PFS (HR, 1.97; 95% CI, 1.39-2.79; P = 0.0001) (homozygous wild-type group) in men with prostate cancer when treated with ADT, however, a higher PFS (HR, 0.68; 95% CI, 0.48-0.96; P = 0.03) when treated with ADT and CYP17A1 inhibitor.

CONCLUSION

The HSD3B1 (1245C) variant is a predictor of ADT plus CYP17A1 inhibitor response in prostate cancer.

Germline HSD3B1 Genetics and Prostate Cancer Outcomes

Dihydrotestosterone synthesis in prostate cancer from adrenal DHEA/DHEA-sulfate requires enzymatic conversion in tumor tissues. 3β-hydroxysteroid dehydrogenase-1 is an absolutely necessary enzyme for such dihydrotestosterone synthesis and is encoded by the gene HSD3B1 which comes in 2 functional inherited forms described in 2013. The adrenal-permissive HSD3B1(1245C) allele allows for rapid dihydrotestosterone synthesis. The adrenal-restrictive HSD3B1(1245A) allele limits androgen synthesis. Studies from multiple cohorts show that adrenal-permissive allele inheritance confers worse outcomes and shorter survival after castration in low-volume prostate cancer and poor outcomes after abiraterone or enzalutamide treatment for castration-resistant prostate cancer. Here, we review the clinical data and implications.

11-Oxygenated androgens in health and disease

The adrenal gland is a source of sex steroid precursors, and its activity is particularly relevant during fetal development and adrenarche. Following puberty, the synthesis of androgens by the adrenal gland has been considered of little physiologic importance. Dehydroepiandrosterone (DHEA) and its sulfate, DHEAS, are the major adrenal androgen precursors, but they are biologically inactive. The second most abundant unconjugated androgen produced by the human adrenals is 11β-hydroxyandrostenedione (11OHA4). 11-Ketotestosterone, a downstream metabolite of 11OHA4 (which is mostly produced in peripheral tissues), and its 5α-reduced product, 11-ketodihydrotestosterone, are bioactive androgens, with potencies equivalent to those of testosterone and dihydrotestosterone. These adrenal-derived androgens all share an oxygen atom on carbon 11, so we have collectively termed them 11-oxyandrogens. Over the past decade, these androgens have emerged as major components of several disorders of androgen excess, such as congenital adrenal hyperplasia, premature adrenarche and polycystic ovary syndrome, as well as in androgen-dependent tumours, such as castration-resistant prostate cancer. Moreover, in contrast to the more extensively studied, traditional androgens, circulating concentrations of 11-oxyandrogens do not demonstrate an age-dependent decline. This Review focuses on the rapidly expanding knowledge regarding the implications of 11-oxyandrogens in human physiology and disease.

HSD3B1 Genotype and Clinical Outcomes in Metastatic Castration-Sensitive Prostate Cancer

Importance

The adrenal-restrictive HSD3B1(1245A) allele limits extragonadal dihydrotestosterone synthesis, whereas the adrenal-permissive HSD3B1(1245C) allele augments extragonadal dihydrotestosterone synthesis. Retrospective studies have suggested an association between the adrenal-permissive allele, the frequency of which is highest in white men, and early development of castration-resistant prostate cancer (CRPC).

Objective

To examine the association between the adrenal-permissive HSD3B1(1245C) allele and early development of CRPC using prospective data.

Design, Setting, and Participants

The E3805 Chemohormonal Therapy vs Androgen Ablation Randomized Trial for Extensive Disease in Prostate Cancer (CHAARTED) was a large, multicenter, phase 3 trial of castration with or without docetaxel treatment in men with newly diagnosed metastatic prostate cancer. From July 28, 2006, through December 31, 2012, 790 patients underwent randomization, of whom 527 had available DNA samples. In this study, the HSD3B1 germline genotype was retrospectively determined in 475 white men treated in E3805 CHAARTED, and clinical outcomes were analyzed by genotype. Data analysis was performed from July 28, 2006, to October 17, 2018.

Interventions

Men were randomized to castration plus docetaxel, 75 mg/m2, every 3 weeks for 6 cycles or castration alone.

Main Outcomes and Measures

Two-year freedom from CRPC and 5-year overall survival, with results stratified by disease volume. Patients were combined across study arms according to genotype to assess the overall outcome associated with genotype. Secondary analyses by treatment arm evaluated whether the docetaxel outcome varied with genotype.

Results

Of 475 white men with DNA samples, 270 patients (56.8%) inherited the adrenal-permissive genotype (≥1 HSD3B1[1245C] allele). Mean (SD) age was 63 (8.7) years. Freedom from CRPC at 2 years was diminished in men with low-volume disease with the adrenal-permissive vs adrenal-restrictive genotype: 51.0% (95% CI, 40.9%-61.2%) vs 70.5% (95% CI, 60.0%-80.9%) (P = .01). Overall survival at 5 years was also worse in men with low-volume disease with the adrenal-permissive genotype: 57.5% (95% CI, 47.4%-67.7%) vs 70.8% (95% CI, 60.3%-81.3%) (P = .03). Hazard ratios were 1.89 (95% CI, 1.13-3.14; P = .02) for CRPC and 1.74 (95% CI, 1.01-3.00; P = .045) for death. There was no association between genotype and outcomes in men with high-volume disease. There was no interaction between genotype and benefit from docetaxel.

Conclusions and Relevance

Inheritance of the adrenal-permissive HSD3B1 genotype is associated with earlier castration resistance and shorter overall survival in men with low-volume metastatic prostate cancer and may help identify men more likely to benefit from escalated androgen receptor axis inhibition beyond gonadal testosterone suppression.

HSD3B1 genotype identifies glucocorticoid responsiveness in severe asthma

Asthma resistance to glucocorticoid treatment is a major health problem with unclear etiology. Glucocorticoids inhibit adrenal androgen production. However, androgens have potential benefits in asthma. HSD3B1 encodes for 3β-hydroxysteroid dehydrogenase-1 (3β-HSD1), which catalyzes peripheral conversion from adrenal dehydroepiandrosterone (DHEA) to potent androgens and has a germline missense-encoding polymorphism. The adrenal restrictive HSD3B1(1245A) allele limits conversion, whereas the adrenal permissive HSD3B1(1245C) allele increases DHEA metabolism to potent androgens. In the Severe Asthma Research Program (SARP) III cohort, we determined the association between DHEA-sulfate and percentage predicted forced expiratory volume in 1 s (FEV1PP). HSD3B1(1245) genotypes were assessed, and association between adrenal restrictive and adrenal permissive alleles and FEV1PP in patients with (GC) and without (noGC) daily oral glucocorticoid treatment was determined (n = 318). Validation was performed in a second cohort (SARP I&II; n = 184). DHEA-sulfate is associated with FEV1PP and is suppressed with GC treatment. GC patients homozygous for the adrenal restrictive genotype have lower FEV1PP compared with noGC patients (54.3% vs. 75.1%; P < 0.001). In patients with the homozygous adrenal permissive genotype, there was no FEV1PP difference in GC vs. noGC patients (73.4% vs. 78.9%; P = 0.39). Results were independently confirmed: FEV1PP for homozygous adrenal restrictive genotype in GC vs. noGC is 49.8 vs. 63.4 (P < 0.001), and for homozygous adrenal permissive genotype, it is 66.7 vs. 67.7 (P = 0.92). The adrenal restrictive HSD3B1(1245) genotype is associated with GC resistance. This effect appears to be driven by GC suppression of 3β-HSD1 substrate. Our results suggest opportunities for prediction of GC resistance and pharmacologic intervention.

Aromatization of natural products by a specialized detoxification enzyme

In plants, lineage-specific metabolites can be created by activities derived from the catalytic promiscuity of ancestral proteins, although examples of recruiting detoxification systems to biosynthetic pathways are scarce. The ubiquitous glyoxalase (GLX) system scavenges the cytotoxic methylglyoxal, in which GLXI isomerizes the α-hydroxy carbonyl in the methylglyoxal-glutathione adduct for subsequent hydrolysis. We show that GLXIs across kingdoms are more promiscuous than recognized previously and can act as aromatases without cofactors. In cotton, a specialized GLXI variant, SPG, has lost its GSH-binding sites and organelle-targeting signal, and evolved to aromatize cyclic sesquiterpenes bearing α-hydroxyketones to synthesize defense compounds in the cytosol. Notably, SPG is able to transform acetylated deoxynivalenol, the prevalent mycotoxin contaminating cereals and foods. We propose that detoxification enzymes are a valuable source of new catalytic functions and SPG, a standalone enzyme catalyzing complex reactions, has potential for toxin degradation, crop engineering and design of novel aromatics.

Sex Hormones and Prostate Cancer

The prostate is an androgen-dependent organ that develops only in male mammals. Prostate cancer is the most common nonskin malignancy in men and the second leading cause of cancer deaths. Metastatic prostate cancer initially retains its androgen dependence, and androgen-deprivation therapy often leads to disease control; however, the cancer inevitably progresses despite treatment as castration-resistant prostate cancer, the lethal form of the disease. Although it was assumed that the cancer became androgen independent during this transition, studies over the last two decades have shown that these tumors evade treatment via mechanisms that augment acquisition of androgens from circulating precursors, increase sensitivity to androgens and androgen precursors, bypass the androgen receptor, or a combination of these mechanisms. This review summarizes the history of prostate cancer research leading to the contemporary view of androgen dependence for prostate cancers and the current treatment approaches based on this modern paradigm.

HSD3B1 Genotypes Conferring Adrenal-Restrictive and Adrenal-Permissive Phenotypes in Prostate Cancer and Beyond

Castration-resistant prostate cancer (PCa) almost invariably occurs after androgen deprivation therapy for metastatic disease and is driven in part by androgen synthesis within the tumor. 3β-hydroxysteroid dehydrogenase isoenzyme-1 catalyzes the conversion of adrenal precursor steroids into potent androgens essential for PCa progression. A common 1245 A→C missense-encoding single nucleotide polymorphism in HSD3B1 (rs1047303), the gene that encodes this enzyme, leads to a more stable protein that is resistant to degradation and thus increased production of potent androgens from adrenal precursors, facilitating castration-resistant PCa development. Consistent with this mechanism, this adrenal-permissive HSD3B1(1245C) genotype is associated with inferior outcomes after androgen deprivation therapy for advanced PCa, and increased sensitivity to pharmacologic blockade of adrenal precursors in metastatic disease. Herein, we review current knowledge of the mechanisms conferred by HSD3B1 genotype to alter androgen physiology and accelerate development of castration-resistant disease and its associations with clinical PCa outcomes. In light of its effect on steroid physiology, we also discuss its potential associations with non-PCa phenotypes.

Calcitriol and cancer therapy: A missed opportunity

The vitamin D receptor is expressed in most tissues of the body - and the cancers that arise from those tissues. The vitamin D signaling pathway is active in those tissues and cancers. This is at least consistent with the hypothesis that perturbing this signaling may have a favorable effect on the genesis and growth of cancers. Epidemiologic data indicate that vitamin D signaling may be important in the initiation and outcome of a number of types of cancer. Many studies have shown that calcitriol (1,25 dihydroxycholecalciferol) and other vitamin D compounds have antiproliferative, pro-apoptotic, anti-cell migration and antiangiogenic activity in a number of preclinical studies in many different cancer types. Unfortunately, the assessment of the activity of calcitriol or other vitamin D analogues in the treatment of cancer, as single agents or in combination with other anticancer agents has been stymied by the failure to adhere to commonly accepted principles of drug development and clinical trials conduct.

HSD3B1 and Response to a Nonsteroidal CYP17A1 Inhibitor in Castration-Resistant Prostate Cancer

IMPORTANCE

The HSD3B1 (1245C) germline variant encodes for a gain-of-function missense in 3β-hydroxysteroid dehydrogenase isoenzyme 1 (3βHSD1) that results in increased dihydrotestosterone synthesis from extragonadal precursors and is predictive of more rapid progression to castration-resistant prostate cancer (CRPC).

OBJECTIVE

To determine whether the HSD3B1 (1245C) genotype is predictive of clinical response to extragonadal androgen ablation with nonsteroidal 17α-hydroxylase/17,20-lyase (CYP17A1) inhibition in men with metastatic CRPC.

DESIGN, SETTING, AND PARTICIPANTS

An observational study of men with metastatic CRPC treated with ketoconazole between June 1998 and December 2012 was conducted at the University of California, San Francisco.

EXPOSURES

Extragonadal androgen ablation with the nonsteroidal CYP17A1 inhibitor ketoconazole among men with metastatic CRPC.

MAIN OUTCOMES AND MEASURES

The primary end points of analysis were duration of ketoconazole therapy and time to disease progression stratified by HSD3B1 genotype. Disease progression was defined as either biochemical or radiographic progression, using the Prostate Cancer Working Group 3 and Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 definitions, respectively. Kaplan-Meier analysis was used to estimate time on therapy and time to disease progression. A log-rank test for trend was used to compare outcomes by HSD3B1 genotype.

RESULTS

A total of 90 men (median [interquartile range] age, 61.5 [55.3-67.0] years) with metastatic CRPC were included in the analysis, with sufficient data to determine duration of ketoconazole therapy and time to disease progression in 88 and 81 patients, respectively. The median duration of therapy increased with the number of inherited HSD3B1 (1245C) variant alleles: 5.0 months (95% CI, 3.4-10.4) for 0 variant alleles; 7.5 months (95% CI, 4.9-19.2) for 1; and 12.3 months (95% CI, 1.8-not reached) for 2 (overall comparison for trend, P = .01). Median progression-free survival also increased with number of HSD3B1 (1245C) variant alleles inherited: 5.4 months (95% CI, 3.7-7.5) for 0 variant alleles; 9.7 months (95% CI, 5.6-32.9) for 1; and 15.2 months (95% CI, 7.8-not reached) for 2 (overall comparison for trend, P = .03).

CONCLUSIONS AND RELEVANCE

Inheritance of the HSD3B1 (1245C) variant allele, which is a predictive biomarker of resistance to castration, is also a predictive biomarker of sensitivity to extragonadal androgen ablation with a nonsteroidal CYP17A1 inhibitor. These findings signal a possible pathway of treatment stratification for patients with prostate cancer.

Loss of an Androgen-Inactivating and Isoform-Specific HSD17B4 Splice Form Enables Emergence of Castration-Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPC) requires tumors to engage metabolic mechanisms that allow sustained testosterone and/or dihydrotestosterone to stimulate progression. 17β-Hydroxysteroid dehydrogenase type 4 (17βHSD4), encoded by HSD17B4, is thought to inactivate testosterone and dihydrotestosterone by converting them to their respective inert 17-keto steroids. Counterintuitively, HSD17B4 expression increases in CRPC and predicts poor prognosis. Here, we show that, of five alternative splice forms, only isoform 2 encodes an enzyme capable of testosterone and dihydrotestosterone inactivation. In contrast with other transcripts, functional expression of isoform 2 is specifically suppressed in development of CRPC in patients. Genetically silencing isoform 2 shifts the metabolic balance toward 17β-OH androgens (testosterone and dihydrotestosterone), stimulating androgen receptor (AR) and CRPC development. Our studies specifically implicate HSD17B4 isoform 2 loss in lethal prostate cancer.

HSD3B1 status as a biomarker of androgen deprivation resistance and implications for prostate cancer

Patients with advanced prostate cancer who receive androgen deprivation therapy (ADT) almost invariably develop castration-resistant disease. The mechanism of resistance is largely based on synthesis of intratumoral androgens from adrenal precursors, requiring enzymatic action of 3β-hydroxysteroid dehydrogenase/Δ^5→4 isomerase 1 (3β-HSD1), encoded by HSD3B1. A nucleotide polymorphism (1245A>C) in HSD3B1 results in a protein variant with increased steady-state levels and subsequently increased androgen synthesis from extragonadal precursors. Multiple clinical studies have shown that patients with the variant allele have significantly worse outcomes after ADT than those without, indicating that HSD3B1 variant status is a predictive biomarker of shortened ADT response. In addition, inheritance of the HSD3B1 variant is associated with extended responses to 17α-hydroxylase/17,20-lyase (CYP17A1) inhibition with a nonsteroidal agent, adding to evidence of increased tumour dependence on extragonadal androgens in patients who inherited the HSD3B1 variant. However, steroidal drugs with a 3β-hydroxyl, Δ⁵-structure, such as abiraterone, are also metabolized by 3β-HSD1, and 5α-abiraterone, a downstream metabolite, has been shown to activate the androgen receptor, potentially driving cancer progression. These data indicate a potential requirement to modify the treatment framework of patients harbouring variant HSD3B1.

CYP17A1-independent production of the neurosteroid-derived 5α-pregnan-3β,6α-diol-20-one in androgen-responsive prostate cancer cell lines under serum starvation and inhibition by Abiraterone

CYP17A1-independent intratumoral steroid hormone synthesis is regarded as one possible explanation for resistance to treatment with the CYP17-inhibitor Abiraterone (Abi). The aim of our study was therefore to investigate the steroid metabolism of prostate cancer cells under serum starvation and the effects of Abi treatment. We assessed steroid metabolism in a panel of prostate cancer cells under serum starvation by radioactivity detector-coupled HPLC and HPLC-ESI-ToF-mass spectrometry after treatment with pregnenolone, progesterone and allopregnanolone. We further evaluated the effects of Abi on steroid metabolism of testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone (DHEA) by enzyme immunoassays (EIAs). Androgen-responsive cell lines metabolized pregnenolone primarily to mitogenic steroid 5α-pregnan-3β,6α-diol-20-one under serum starvation. Co-administration of Abi lead to detectable concentrations of the Abi metabolite Δ⁴-Abi (D4A), known to inhibit enzymes other than CYP17A1 in steroid metabolism. In addition, co-administration of Abi abrogated pregnenolone metabolism and resulted in a CYP17A1-independent significant increase of DHEA (13- to >100-fold) and DHT (2.5-fold) in androgen-responsive cells. Our results demonstrate the CYP17A1-independent formation of 5α-pregnan-3β,6α-diol-20-one by androgen-responsive prostate cancer cells under serum starvation and its inhibition by Abi. Its metabolism from pregnenolone suggests a major steroidogenesis shift in these cells, hinting at a neuroendocrine transdifferentiation phenomenon. The marked increase of DHEA levels by Abi resembles the steroidogenic pathways in nervous tissue, in a manner that precludes CYP17A1 activity. To which extent these processes are responsible or involved in the development of resistance to Abi, needs to be further elucidated.

ACSL3 promotes intratumoral steroidogenesis in prostate cancer cells

Long‐chain acyl‐coenzyme A (CoA) synthetase 3 (ACSL3) is an androgen‐responsive gene involved in the generation of fatty acyl‐CoA esters. ACSL3 is expressed in both androgen‐sensitive and castration‐resistant prostate cancer (CRPC). However, its role in prostate cancer remains elusive. We overexpressed ACSL3 in androgen‐dependent LNCaP cells and examined the downstream effectors of ACSL3. Furthermore, we examined the role of ACSL3 in the androgen metabolism of prostate cancer. ACSL3 overexpression led to upregulation of several genes such as aldo‐keto reductase 1C3 (AKR1C3) involved in steroidogenesis, which utilizes adrenal androgen dehydroepiandrosterone sulfate (DHEAS) as substrate, and downregulated androgen‐inactivating enzyme UDP‐glucuronosyltransferase 2 (UGT2B). Exposure to DHEAS significantly increased testosterone levels and cell proliferative response in ACSL3‐overexpressing cells when compared to that in control cells. A public database showed that ACSL3 level was higher in CRPC than in hormone‐sensitive prostate cancer. CRPC cells showed an increased expression of ACSL3 and an expression pattern of AKR1C3 and UGT2B similar to ACSL3‐overexpressing cells. DHEAS stimulation significantly promoted the proliferation of CRPC cells when compared to that of LNCaP cells. These findings suggest that ACSL3 contributes to the growth of CRPC through intratumoral steroidogenesis (i.e. promoting androgen synthesis from DHEAS and preventing the catabolism of active androgens).

Development and validation of a novel LC-MS/MS method for simultaneous determination of abiraterone and its seven steroidal metabolites in human serum: Innovation in separation of diastereoisomers without use of a chiral column

Abiraterone acetate (AA), the prodrug of abiraterone, is FDA-approved for the treatment of castration-resistant prostate cancer. Abiraterone is metabolized in patients to a more potent analogue, D4A. However, we have recently reported that this analogue is further metabolized to additional metabolites in patients treated with AA. Here, we present a liquid chromatography-tandem mass spectrometry method developed to resolve and detect abiraterone and its seven metabolites in human serum using an AB Sciex Qtrap 5500 mass analyzer coupled with a Shimadzu Nexera UPLC station. Analytes and the internal standard (abiraterone-d4) were extracted from human serum using the liquid-liquid extraction procedure. The analytes were separated using a Zorbax Eclipse Plus C18 150×2.1mm, 3.5μm column at 40°C and an isocratic mobile phase 35% A (0.1% formic acid in water), 65% B (0.1% formic acid in methanol:acetonitrile; 60:40). Electrospray ionization in positive mode was applied with multiple reaction monitoring in a total run time of 13min. Abiraterone detection was linear in the range 2-400ng/mL and all metabolites from 0.1-20ng/mL. The method was validated following US FDA guidelines for bioanalytical method validation, and all the metabolite results were within the acceptance limits. Despite the similarity in structure and mass transition between the metabolites, the validated method separated all the metabolites, including diastereomers, to allow accurate identification and quantitation of each compound.

CXCL13 is androgen-responsive and involved in androgen induced prostate cancer cell migration and invasion

Androgen receptor (AR) is a key transcription factor playing a critical role in prostate cancer (PCa) initiation and progression. However, the molecular mechanisms of AR action in prostate cancer are not very clear. CXCL13, known as B cell attracting chemokine1 (BCA-1), is a member of CXC chemokine family and relevant to cancer metastasis. This study shows that CXCL13 is an androgen-responsive gene and involved in AR-induced PCa cell migration and invasion. In clinical specimens, expression of CXCL13 in PCa tissues is markedly higher than that in adjacent normal tissues. In cultures, expression of CXCL13 is up-regulated by androgen-AR axis at both mRNA and protein levels. Furthermore, Chip-Seq assay identifies canonical androgen responsive elements (ARE) at CXCL13 enhancer and dual-luciferase reporter assays reveals that the ARE is highly responsive to androgen while mutations of the ARE abolish the reporter activity. Additional chromatin immunoprecipitation (ChIP) assays also identify that the ARE presents androgen responsiveness. In addition, CXCL13 promotes G2/M phase transition by increasing Cyclin B1 levels in PCa cells. Functional studies demonstrate that reducing endogenous CXCL13 expression in LNCaP cells largely weakens androgen-AR axis induced cell migration and invasion. Taken together, our study implicates for the first time that CXCL13 is an AR target gene and involved in AR-mediated cell migration and invasion in primary PCa.

Steroid hormone receptors and prostate cancer: role of structural dynamics in therapeutic targeting

Steroid hormone receptors (SHRs) act in cell type- and gene-specific manner through interactions with coregulatory proteins to regulate numerous physiological and pathological processes at the level of gene regulation. Binding of steroid receptor modulator (SRM) ligand leads to allosteric changes in SHR to exert positive or negative effects on the expression of target genes. Due, in part, to the fact that current SRMs generally target ligand binding domain (LBD)/AF2 and neglect intrinsically disordered (ID) N-terminal domain (NTD)/AF1, clinically relevant SRMs lack selectivity and are also prone to the development of resistance over time. Therefore, to maximize the efficacy of SHR-based therapeutics, the possibility of developing unique modulators that act to control AF1 activity must be considered. Recent studies targeting androgen receptor's (AR's) ID AF1 domain for the castration-resistant prostate cancer has provided the possibility of therapeutically targeting ID NTD/AF1 surfaces by allosteric modulations to achieve desired effects. In this review article, we discuss how inter- and intra- molecular allosteric regulations controlled by AR's structural flexibility and dynamics particularly the ID NTD/AF1 is an emerging area of investigation, which could be exploited for drug development and therapeutic targeting of prostate cancer.

Aberrant corticosteroid metabolism in tumor cells enables GR takeover in enzalutamide resistant prostate cancer

Prostate cancer is driven by androgen stimulation of the androgen receptor (AR). The next-generation AR antagonist, enzalutamide, prolongs survival, but resistance and lethal disease eventually prevail. Emerging data suggest that the glucocorticoid receptor (GR) is upregulated in this context, stimulating expression of AR-target genes that permit continued growth despite AR blockade. However, countering this mechanism by administration of GR antagonists is problematic because GR is essential for life. We show that enzalutamide treatment in human models of prostate cancer and patient tissues is accompanied by a ubiquitin E3-ligase, AMFR, mediating loss of 11β-hydroxysteroid dehydrogenase-2 (11β-HSD2), which otherwise inactivates cortisol, sustaining tumor cortisol concentrations to stimulate GR and enzalutamide resistance. Remarkably, reinstatement of 11β-HSD2 expression, or AMFR loss, reverses enzalutamide resistance in mouse xenograft tumors. Together, these findings reveal a surprising metabolic mechanism of enzalutamide resistance that may be targeted with a strategy that circumvents a requirement for systemic GR ablation.

Androgen Receptor: A Complex Therapeutic Target for Breast Cancer

Molecular and histopathological profiling have classified breast cancer into multiple sub-types empowering precision treatment. Although estrogen receptor (ER) and human epidermal growth factor receptor (HER2) are the mainstay therapeutic targets in breast cancer, the androgen receptor (AR) is evolving as a molecular target for cancers that have developed resistance to conventional treatments. The high expression of AR in breast cancer and recent discovery and development of new nonsteroidal drugs targeting the AR provide a strong rationale for exploring it again as a therapeutic target in this disease. Ironically, both nonsteroidal agonists and antagonists for the AR are undergoing clinical trials, making AR a complicated target to understand in breast cancer. This review provides a detailed account of AR’s therapeutic role in breast cancer.

Inhibition of the hexosamine biosynthetic pathway promotes castration-resistant prostate cancer

The precise molecular alterations driving castration-resistant prostate cancer (CRPC) are not clearly understood. Using a novel network-based integrative approach, here, we show distinct alterations in the hexosamine biosynthetic pathway (HBP) to be critical for CRPC. Expression of HBP enzyme glucosamine-phosphate N-acetyltransferase 1 (GNPNAT1) is found to be significantly decreased in CRPC compared with localized prostate cancer (PCa). Genetic loss-of-function of GNPNAT1 in CRPC-like cells increases proliferation and aggressiveness, in vitro and in vivo. This is mediated by either activation of the PI3K-AKT pathway in cells expressing full-length androgen receptor (AR) or by specific protein 1 (SP1)-regulated expression of carbohydrate response element-binding protein (ChREBP) in cells containing AR-V7 variant. Strikingly, addition of the HBP metabolite UDP-N-acetylglucosamine (UDP-GlcNAc) to CRPC-like cells significantly decreases cell proliferation, both in-vitro and in animal studies, while also demonstrates additive efficacy when combined with enzalutamide in-vitro. These observations demonstrate the therapeutic value of targeting HBP in CRPC.

The molecular alterations driving anti-androgen resistance in prostate cancer are unclear. Here, the authors show, using a network-based approach, that inhibition of the hexosamine biosynthetic pathway is necessary to develop resistance and that increasing the activity of the pathway enhances the anti-androgen response.

Mechanisms of resistance in castration-resistant prostate cancer (CRPC)

Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies.

Predictors of early androgen deprivation treatment failure in prostate cancer with bone metastases

Approximately 15% of men with hormone naïve metastatic prostate cancer primarily fail to respond to androgen deprivation treatment (ADT). The reason why the response to ADT differs in this subgroup of men with prostate cancer remains unclear. The aim of this study was to describe the characteristics of these men and to thereby define predictors of early ADT failure in prostate cancer patients with bone metastases. The study was based on 915 men from the prospective randomized multicenter trial (no. 5) conducted by the Scandinavian Prostate Cancer Group comparing parenteral estrogen with total androgen blockade. Early ADT failure was defined as death from metastatic prostate cancer within 12 months after the start of ADT. Multivariate logistic regression models were applied to identify clinical predictors of early ADT failure. Ninety‐four (10.3%) men were primarily nonresponders to ADT. Independent predictors of early ADT failure were poor Eastern Cooperative Oncology Group performance status (PS), analgesic consumption, low hemoglobin, and high Soloway score (extent of disease observed on the scan), in where patients with poor PS and/or high analgesic consumption had a threefold risk of early ADT failure. Not significantly factors related to early ADT failure were age, treatment, cardiovascular comorbidity, T category, grade of malignancy, serum estrogen level, and SHBG at enrolment. We analyzed characteristics of a subgroup of patients who primarily failed to respond to ADT. Four independent clinical predictors of early ADT failure could be defined, and men exhibiting these features should be considered for an alternative treatment.

Role of BioResponse 3,3'-Diindolylmethane in the Treatment of Human Prostate Cancer: Clinical Experience

Castration-resistant prostate cancer (CRPC) progression after androgen deprivation therapy shows upregulated expression of androgen receptor (AR) splice variants, induced epithelial-to-mesenchymal transition phenotypes and enhanced stem cell characteristics, all of which are associated with resistance to enzalutamide. Since there is no curative treatment for CRPC, innovative treatments are urgently needed. In our recent study, we found that resistance to enzalutamide was partly due to deregulated expression of microRNAs such as miR-34a, miR-124, miR-27b, miR-320 and let-7, which play important roles in regulating AR and stem cell marker gene expression that appears to be linked with resistance to enzalutamide. Importantly, we found that BioResponse 3,3'-diindolylmethane (BR-DIM) treatment in vitro and in vivo caused downregulation in the expression of wild-type AR. The AR splice variants, Lin28B and EZH2, appear to be deregulated through the re-expression of let-7, miR-27b, miR-320 and miR-34a in human prostate cancer (PCa). BR-DIM administered in clinical trials was well tolerated, and 93% of patients had detectable prostatic DIM levels. The inhibitory effects of BR-DIM on AR and AR target gene such as prostate-specific antigen were also observed in the clinical trial. Our preclinical and clinical studies provide the scientific basis for a 'proof-of-concept' clinical trial in CRPC patients treated with enzalutamide in combination with BR-DIM. This strategy could be expanded in future clinical trials in patients with PCa to determine whether or not they could achieve a better treatment outcome which could be partly mediated by delaying or preventing the development of CRPC.

Targeting molecular resistance in castration-resistant prostate cancer

Multiple mechanisms of resistance contribute to the inevitable progression of hormone-sensitive prostate cancer to castration-resistant prostate cancer (CRPC). Currently approved therapies for CRPC include systemic chemotherapy (docetaxel and cabazitaxel) and agents targeting the resistance pathways leading to CRPC, including enzalutamide and abiraterone. While there is significant survival benefit, primary and secondary resistance to these therapies develops rapidly. Up to one-third of patients have primary resistance to enzalutamide and abiraterone; the remaining patients eventually progress on treatment. Understanding the mechanisms of resistance resulting in progression as well as identifying new targetable pathways remains the focus of current prostate cancer research. We review current knowledge of mechanisms of resistance to the currently approved treatments, development of adjunctive therapies, and identification of new pathways being targeted for therapeutic purposes.

Biological relevance of Hsp90-binding immunophilins in cancer development and treatment

Immunophilins are a family of intracellular receptors for immunosuppressive drugs. Those immunophilins that are related to immunosuppression are the smallest proteins of the family, i.e., FKBP12 and CyPA, whereas the other members of the family have higher molecular weight because the show additional domains to the drug-binding site. Among these extra domains, the TPR-domain is perhaps the most relevant because it permits the interaction of high molecular weight immunophilins with the 90-kDa heat-shock protein, Hsp90. This essential molecular chaperone regulates the biological function of several protein-kinases, oncogenes, protein phosphatases, transcription factors and cofactors . Hsp90-binding immunophilins where first characterized due to their association with steroid receptors. They regulate the cytoplasmic transport and the subcellular localization of these and other Hsp90 client proteins, as well as transcriptional activity, cell proliferation, cell differentiation and apoptosis. Hsp90-binding immunophilins are frequently overexpressed in several types of cancers and play a key role in cell survival. In this article we analyze the most important biological actions of the best characterized Hsp90-binding immunophilins in both steroid receptor function and cancer development and discuss the potential use of these immunophilins for therapeutic purposes as potential targets of specific small molecules.

Identification of a long non-coding RNA as a novel biomarker and potential therapeutic target for metastatic prostate cancer

Metastatic prostate cancer (PCa) is still an incurable disease. Long non-coding RNAs (lncRNAs) may be an overlooked source of cancer biomarkers and therapeutic targets. We therefore performed RNA sequencing on paired metastatic/non-metastatic PCa xenografts derived from clinical specimens. The most highly up-regulated transcript was LOC728606, a lncRNA now designated PCAT18. PCAT18 is specifically expressed in the prostate compared to 11 other normal tissues (p<0.05) and up-regulated in PCa compared to 15 other neoplasms (p<0.001). Cancer-specific up-regulation of PCAT18 was confirmed on an independent dataset of PCa and benign prostatic hyperplasia samples (p<0.001). PCAT18 was detectable in plasma samples and increased incrementally from healthy individuals to those with localized and metastatic PCa (p<0.01). We identified a PCAT18-associated expression signature (PES), which is highly PCa-specific and activated in metastatic vs. primary PCa samples (p<1E-4, odds ratio>2). The PES was significantly associated with androgen receptor (AR) signalling. Accordingly, AR activation dramatically up-regulated PCAT18 expression in vitro and in vivo. PCAT18 silencing significantly (p<0.001) inhibited PCa cell proliferation and triggered caspase 3/7 activation, with no effect on non-neoplastic cells. PCAT18 silencing also inhibited PCa cell migration (p<0.01) and invasion (p<0.01). These results position PCAT18 as a potential therapeutic target and biomarker for metastatic PCa.

Androgen metabolism in prostate cancer: from molecular mechanisms to clinical consequences

Despite our most vigorous efforts, prostate cancer remains the second leading cause of cancer death in men. Understanding the intricacies of androgen metabolism is vital to finding therapeutic targets, particularly with progression of advanced prostate cancer after initial hormone therapy, where adrenal precursors are involved. Such is the case with castration-resistant prostate cancer, where adrenal androgens, for example, dehydroepiandrosterone, are a source for intratumoural synthesis of dihydrotestosterone. As prostate cancer progresses, androgen metabolism changes due to altered expression of steroidogenic enzymes and mutations in the components of the steroidogenic machinery. These alterations sustain disease and allow progression; mechanistically, they may also enable development of hormone therapy resistance. With the development of the newer agents, abiraterone acetate and enzalutamide, efforts have been made to better define the basis for response and resistance. This work can be carried out in cell lines, animal models, as well as with ex vivo analysis of tissues obtained from patients. Efforts to further elucidate the finer details of the steroidogenic pathway are necessary to move toward a curative paradigm for patients with localised disease at high risk for recurrence.

Pomegranate extracts impact the androgen biosynthesis pathways in prostate cancer models in vitro and in vivo

Castration-resistant prostate cancer (CRPC) remains largely dependent on androgen receptor (AR). Residual tissue androgens are consistently detected within CRPC tumors and play a critical role in facilitating AR-mediated signaling pathways which lead to disease progression. Testosterone and dihydrotestosterone (DHT) are the major androgens detected in tumors. They are produced through three biosynthesis pathways: Δ(4), Δ(5), and backdoor pathways. Both androgens bind to and stimulate AR activation. The current study investigates the effects of pomegranate extracts (POM) and their ability to inhibit androgen biosynthesis using PCa cell lines (22RV1 and LNCaP) in vitro as well as the PTEN knockout mouse model representing prostate cancer. Steroids were extracted using ethyl acetate or solid phase extraction, and then analyzed by UPLC/MS/MS. The results showed that POM (0-12μg/mL) reduced the production of testosterone, DHT, DHEA, androstenedione, androsterone, and pregnenolone in both cell lines. In addition our in vivo data supports this observation with a reduction in serum steroids determined after 20 weeks of POM treatment (0.17 g/L in drinking water). In accordance with these results, Western blotting of cell lysates and tPSA analysis determined that PSA was significantly decreased by the treatment of POM. Interestingly, AKR1C3 and AR levels were shown to be increased in both cell lines, perhaps as a negative feedback effect in response to steroid inhibition. Overall, these results provide mechanistic evidence to support the rationale for recent clinical reports describing efficacy of POM in CRPC patients.

Androgen synthesis inhibitors in the treatment of castration-resistant prostate cancer

Suppression of gonadal testosterone synthesis represents the standard first line therapy for treatment of metastatic prostate cancer. However, in the majority of patients who develop castration-resistant prostate cancer (CRPC), it is possible to detect persistent activation of the androgen receptor (AR) through androgens produced in the adrenal gland or within the tumor itself. Abiraterone acetate was developed as an irreversible inhibitor of the dual functional cytochrome P450 enzyme CYP17 with activity as a 17α-hydroxylase and 17,20-lyase. CYP17 is necessary for production of nongonadal androgens from cholesterol. Regulatory approval of abiraterone in 2011, based on a phase III trial showing a significant improvement in overall survival (OS) with abiraterone and prednisone versus prednisone, represented proof of principle that targeting AR is essential for improving outcomes in men with CRPC. Inhibition of 17α-hydroxylase by abiraterone results in accumulation of upstream mineralocorticoids due to loss of cortisol-mediated suppression of pituitary adrenocorticotropic hormone (ACTH), providing a rationale for development of CYP17 inhibitors with increased specificity for 17,20-lyase (orteronel, galeterone and VT-464) that can potentially be administered without exogenous corticosteroids. In this article, we review the development of abiraterone and other CYP17 inhibitors; recent studies with abiraterone that inform our understanding of clinical parameters such as drug effects on quality-of-life, potential early predictors of response, and optimal sequencing of abiraterone with respect to other agents; and results of translational studies providing insights into resistance mechanisms to CYP17 inhibitors leading to clinical trials with drug combinations designed to prolong abiraterone benefit or restore abiraterone activity.

SGK3 is an androgen-inducible kinase promoting prostate cancer cell proliferation through activation of p70 S6 kinase and up-regulation of cyclin D1

Both androgen and phosphatidylinositol 3-kinase (PI3K) signaling are critical for cell proliferation of androgen receptor (AR)-positive prostate cancer cells, but the underlying mechanisms are still not fully understood. Here we report that serum- and glucocorticoid-inducible kinase 3 (SGK3), a Ser/Thr kinase functioning downstream of PI3K, is an AR transcriptional target and promotes prostate cancer cell proliferation. SGK3 expression is up-regulated by androgen DHT via AR. We identified an AR-binding region at the sgk3 locus, which confers androgen responsiveness of sgk3 promoters. Interestingly, we found that androgen/AR-dependent SGK3 expression requires estrogen receptor (ER) (including both isoforms, ERα and ERβ). Depletion of ER blocked DHT-induced SGK3 expression. Functionally, knockdown of SGK3 expression significantly decreased LNCaP prostate cancer cell proliferation by inhibiting G1 to S phase cell cycle progression. We further provided evidence that SGK3 promotes p70 S6 kinase (p70S6K) activation and increases cyclin D1 levels. In summary, our study identifies SGK3 as an AR target and provides a novel androgen-induced cell proliferation mechanism mediated by the AR-SGK3-p70S6K-cyclin D1 pathway in prostate cancer cells.