Semaphorin 3C promotes de novo steroidogenesis in prostate cancer cells.

Intratumoral androgen biosynthesis contributes to castration-resistant prostate cancer progression in patients treated with androgen deprivation therapy. The molecular mechanisms by which castration-resistant prostate cancer acquires the capacity for androgen biosynthesis to bypass androgen deprivation therapy are not entirely known. Here, we show that semaphorin 3C, a secreted signaling protein that is highly expressed in castration-resistant prostate cancer, can promote steroidogenesis by altering the expression profile of key steroidogenic enzymes. Semaphorin 3C not only upregulates enzymes required for androgen synthesis from dehydroepiandrosterone or de novo from cholesterol but also simultaneously downregulates enzymes involved in the androgen inactivation pathway. These changes in gene expression correlate with increased production of androgens induced by semaphorin 3C in prostate cancer model cells. Moreover, semaphorin 3C upregulates androgen synthesis in LNCaP cell-derived xenograft tumors, likely contributing to the enhanced in vivo tumor growth rate post castration. Furthermore, semaphorin 3C activates sterol regulatory element-binding protein, a transcription factor that upregulates enzymes involved in the synthesis of cholesterol, a sole precursor for de novo steroidogenesis. The ability of semaphorin 3C to promote intratumoral androgen synthesis may be a key mechanism contributing to the reactivation of the androgen receptor pathway in castration-resistant prostate cancer, conferring continued growth under androgen deprivation therapy. These findings identify semaphorin 3C as a potential therapeutic target for suppressing intratumoral steroidogenesis.

Extracellular vesicles from biological fluids as potential markers in castration resistant prostate cancer.

PURPOSE: Extracellular vesicles (EV) secreted from cancer cells are present in various biological fluids, carrying distinctly different cellular components compared to normal cells, and have great potential to be used as markers for disease initiation, progression, and response to treatment. This under-utilised tool provides insights into a better understanding of prostate cancer. METHODS: EV from serum and urine of healthy men and castration-resistant prostate cancer (CRPC) patients were isolated and characterised by transmission electron microscopy, particle size analysis, and western blot. Proteomic and cholesterol liquid chromatography-mass spectrometry (LC-MS) analyses were conducted. RESULTS: There was a successful enrichment of small EV/exosomes isolated from serum and urine. EV derived from biological fluids of CRPC patients had significant differences in composition when compared with those from healthy controls. Analysis of matched serum and urine samples from six prostate cancer patients revealed specific EV proteins common in both types of biological fluid for each patient. CONCLUSION: Some of the EV proteins identified from our analyses have potential to be used as CRPC markers. These markers may depict a pattern in cancer progression through non-invasive sample collection.

1α,25-Dihydroxyvitamin D3 synergistically enhances anticancer effects of ginsenoside Rh2 in human prostate cancer cells.

1α,25-dihydroxyvitamin D3 (1,25(OH)2D3, commonly known as calcitriol), the most active metabolite of vitamin D3, and ginsenoside Rh2 can regulate cellular differentiation and proliferation proteins. The purpose of the present study was to assess the effect of 1,25(OH)2D3 on the anticancer activities of Rh2 in human prostate cancer cells such as androgen-dependent LNCaP and androgen-independent C4-2 in vitro. The effects of treatment with 1,25(OH)2D3 or Rh2, either alone or in combination, on prostate cancer cells were evaluated through tetrazolium-based cell viability assay, BrdU cell proliferation rate estimation assay, and Western blot protein expression analyses of nuclear receptors (androgen receptor and vitamin D receptors) and apoptotic proteins (Bcl-2, Bax, and Caspase 3). The Combination Indices (CI) and Dose Reduction Indices (DRI) of 1,25(OH)2D3 and Rh2 were calculated to determine synergistic anticancer activity using Calcusyn software (Biosoft, Cambridge, UK). The cell viability assay data indicate that Rh2 treatment alone inhibited cell viability in a concentration-dependent manner and the addition of 10 nM 1,25(OH)2D3 to Rh2 significantly enhanced its ability to reduce cell viability up to 80 % in both the cell lines. Similarly, addition of 10 nM 1,25(OH)2D3 to Rh2 significantly lowered its IC50 values for cell proliferation from the range of 32-65 µM to 14-8 µM in LNCaP and C4-2 cells. In addition, protein expression analyses indicated that the combined treatment with Rh2 and 1,25(OH)2D3 led to greater downregulation of androgen receptor expression compared to single agent exposure. Similarly, the presence of 1,25(OH)2D3 synergistically increased the pro-apoptotic actions of Rh2 in both the cell lines. Overall, 1,25(OH)2D3 augments the Rh2-mediated anticancer effects through stimulating apoptosis and reduced cell proliferation which suggests that synergism of this combination may lead to potential lower need of the active vitamin D3 and limited toxicity from it.

Characterization of Precursor-Dependent Steroidogenesis in Human Prostate Cancer Models.

Castration-resistant prostate tumors acquire the independent capacity to generate androgens by upregulating steroidogenic enzymes or using steroid precursors produced by the adrenal glands for continued growth and sustainability. The formation of steroids was measured by liquid chromatography-mass spectrometry in LNCaP and 22Rv1 prostate cancer cells, and in human prostate tissues, following incubation with steroid precursors (22-OH-cholesterol, pregnenolone, 17-OH-pregnenolone, progesterone, 17-OH-progesterone). Pregnenolone, progesterone, 17-OH-pregnenolone, and 17-OH-progesterone increased C21 steroid (5-pregnan-3,20-dione, 5-pregnan-3,17-diol-20-one, 5-pregnan-3-ol-20-one) formation in the backdoor pathway, and demonstrated a trend of stimulating dihydroepiandrosterone or its precursors in the backdoor pathway in LNCaP and 22Rv1 cells. The precursors differentially affected steroidogenic enzyme messenger RNA (mRNA) expressions in the cell lines. The steroidogenesis following incubation of human prostate tissue with 17-OH-pregnenolone and progesterone produced trends similar to those observed in cell lines. Interestingly, the formation of C21 steroids from classical pathway was not stimulated but backdoor pathway steroids (e.g., 5-pregnan-3,20-dione, 5-pregnan-3-ol-20-one) were elevated following incubations with prostate tissues. Overall, C21 steroids were predominantly formed in the classical as well as backdoor pathways, and steroid precursors induced a diversion of steroidogenesis to the backdoor pathway in both cell lines and human prostate tissue, and influenced adaptive steroidogenesis to form C21 steroids.

Targeting Binding Function-3 of the Androgen Receptor Blocks Its Co-Chaperone Interactions, Nuclear Translocation, and Activation.

The development of new antiandrogens, such as enzalutamide, or androgen synthesis inhibitors like abiraterone has improved patient outcomes in the treatment of advanced prostate cancer. However, due to the development of drug resistance and tumor cell survival, a majority of these patients progress to the refractory state of castration-resistant prostate cancer (CRPC). Thus, newer therapeutic agents and a better understanding of their mode of action are needed for treating these CRPC patients. We demonstrated previously that targeting the Binding Function 3 (BF3) pocket of the androgen receptor (AR) has great potential for treating patients with CRPC. Here, we explore the functional activity of this site by using an advanced BF3-specific small molecule (VPC-13566) that was previously reported to effectively inhibit AR transcriptional activity and to displace the BAG1L peptide from the BF3 pocket. We show that VPC-13566 inhibits the growth of various prostate cancer cell lines, including an enzalutamide-resistant cell line, and reduces the growth of AR-dependent prostate cancer xenograft tumors in mice. Importantly, we have used this AR-BF3 binder as a chemical probe and identified a co-chaperone, small glutamine-rich tetratricopeptide repeat (TPR)-containing protein alpha (SGTA), as an important AR-BF3 interacting partner. Furthermore, we used this AR-BF3-directed small molecule to demonstrate that inhibition of AR activity through the BF3 functionality can block translocation of the receptor into the nucleus. These findings suggest that targeting the BF3 site has potential clinical importance, especially in the treatment of CRPC and provide novel insights on the functional role of the BF3 pocket. Mol Cancer Ther; 15(12); 2936-45. ©2016 AACR.

Calcitriol in Combination Therapy for Prostate Cancer: Pharmacokinetic and Pharmacodynamic Interactions.

Epidemiological studies indicate that vitamin D insufficiency could have an etiological role in prostate cancer. In addition, calcitriol, used in combination with currently available drugs, has the potential to potentiate their anticancer effects or act synergistically by inhibiting distinct mechanisms involved in prostate cancer growth. Clinical data have not yet provided sufficient evidence to demonstrate benefit of vitamin D due to the limited and underpowered studies that have been published to date. Here, we review the preclinical and clinical studies that describe the activity of calcitriol, applied either alone or in combination and assessed the mechanistic basis of pharmacodynamic and pharmacokinetic interactions with calcitriol. Important considerations for calcitriol use in combination therapy with respect to safety and clinical outcomes have been discussed. Many of these combinations have therapeutic potential for the treatment of several cancer types and it is anticipated that future clinical research will put emphasis on well­designed clinical trials to establish efficacy.

The effect of pomegranate fruit extract on testosterone-induced BPH in rats.

BACKGROUND: Benign prostatic hyperplasia (BPH) affects many men after the age of 50 years. Inflammation and oxidative stress along with apoptotic changes are thought to play an important role in the pathology of BPH. Pomegranate contains a variety of polyphenolic compounds that have been studied in a medley of diseases for their anti-oxidant, anti-inflammatory and pro-apoptotic properties. Therefore, this study examined the effect of Pomegranate Fruit Extract (PFE) on the development of BPH using a testosterone-induced BPH model in rats. METHODS: A total of 48 rats were randomly divided into six groups of eight, one group served as the control, BPH was induced by testosterone 3 mg/kg S.C. daily in four groups, three of them received PFE by oral gavage daily at doses of 25, 50, and 100 mg/kg respectively, while one group received PFE at a dose of 50 mg/kg without induction of BPH. RESULTS: PFE at a dose of 100 mg/kg was the most effective in decreasing testosterone-induced increase in prostate weight, prostate weight/body weight ratio, and PAP levels by 30.8%, 55%, and 68% respectively and in preventing the accompanying histological changes. In the BPH model, testosterone significantly decreased GSH, SOD, and CAT to 0.45, 0.64, and 0.88 of the control group values respectively, and significantly increased MDA by >6-fold. In combination with testosterone, PFE dosed at 100 mg/kg significantly increased GSH, SOD, and CAT to 0.83, 0.92, and 0.93 of the control group values respectively, whereas MDA was significantly decreased by 72% compared with the testosterone treated group. In addition to this, at the range of doses studied, PFE lowered COX-II, iNOS, Ki-67 expression, and increased apoptotic index. CONCLUSION: The current findings elucidate the effectiveness of PFE in preventing testosterone-induced BPH in rats. This could be attributed, at least partly, to its anti-oxidant, anti-inflammatory, and pro-apoptotic properties.

Anticancer activity of a novel selective CYP17A1 inhibitor in preclinical models of castrate-resistant prostate cancer.

VT-464 is a novel, nonsteroidal, small-molecule CYP17A1 inhibitor with 17,20-lyase selectivity. This study evaluates the anticancer activity of VT-464 compared with abiraterone (ABI) in castrate-resistant prostate cancer cell lines and xenograft models that are enzalutamide (ENZ)-responsive (C4-2) or ENZ-resistant (MR49C, MR49F). In vitro, androgen receptor (AR) transactivation was assessed by probasin luciferase reporter, whereas AR and AR-regulated genes and steroidogenic pathway enzymes were assessed by Western blot and/or qRT-PCR. The MR49F xenograft model was used to compare effects of oral VT-464 treatment to vehicle and abiraterone acetate (AA). Steroid concentrations were measured using LC-MS chromatography. VT-464 demonstrated a greater decrease in AR transactivation compared with ABI in C4-2 and both ENZ-resistant cell lines. At the gene and protein level, VT-464 suppressed the AR axis to a greater extent compared with ABI. Gene transcripts StAR, CYP17A1, HSD17B3, and SRD5A1 increased following treatment with ABI and to a greater extent with VT-464. In vivo, intratumoral androgen levels were significantly lower after VT-464 or AA treatment compared with vehicle, with the greatest decrease seen with VT-464. Similarly, tumor growth inhibition and PSA decrease trends were greater with VT-464 than with AA. Finally, an AR-antagonist effect of VT-464 independent of CYP17A1 inhibition was observed using luciferase reporter assays, and a direct interaction was confirmed using an AR ligand binding domain biolayer interferometry. These preclinical results suggest greater suppression of the AR axis with VT-464 than ABI that is likely due to both superior selective suppression of androgen synthesis and AR antagonism.

Next-generation steroidogenesis inhibitors, dutasteride and abiraterone, attenuate but still do not eliminate androgen biosynthesis in 22RV1 cells in vitro.

Castration resistant prostate cancer (CRPC) is often lethal and inevitably develops after androgen ablation therapy. However, in the majority of cases it remains androgen dependent. CRPC tumors have the ability to synthesize their own androgens from cholesterol by engaging in de novo steroidogenesis. We investigated the potential of 22RV1 prostate cancer cells to convert the supplemented steroid precursors within this pathway under the effects of current clinical steroidogenesis inhibitors such as abiraterone and dutasteride, either alone or in combination. Under steroid starved conditions, enzymes responsible for de novo steroidogenesis were upregulated. Testosterone and dihydrotestosterone (DHT) were formed by using both dehydroepiandrosterone (DHEA) and progesterone as substrates. Formation of testosterone and DHT was higher following incubation with DHEA compared to progesterone. Progesterone decreased the mRNA expression of enzymes responsible for steroidogenesis. Abiraterone treatment decreased testosterone production but increased several precursor steroids in both classical and backdoor pathways in the presence of progesterone. In contrast, the DHT levels were elevated following treatment with abiraterone when progesterone was absent. Dutasteride decreased the formation of testosterone, DHT and precursor steroids in the backdoor pathway but increased steroid precursors in the classical steroidogenesis pathway. The combination of abiraterone and dutasteride decreased testosterone and DHT in the presence of progesterone but increased DHT in the absence of progesterone. Abiraterone inhibited androgen receptor (AR) activation but not to the same extent as MDV3100. However, abiraterone and dutasteride treatment, either alone or in combination, were more effective in decreasing prostate specific antigen secretion into the media than MDV3100. Thus, while interventions with these drugs alone or in combination fail to completely inhibit steroidogenesis in the 22RV1 cells, the combined inhibition of androgen production and blockade of AR can exceed the effect of MDV3100. Further characterization of bypass mechanisms that may develop as a response to these inhibitors is necessary to achieve optimal suppression of testosterone and DHT synthesis as a part of therapeutic regimens for the treatment of CRPC.

Ginsenoside-mediated blockade of 1α,25-dihydroxyvitamin D3 inactivation in human liver and intestine in vitro.

The beneficial effects of vitamin D3 are exerted through 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], the dihydroxy metabolite of vitamin D3. Hepatic and intestinal biotransformation of 1α,25(OH)2D3 and modifiers of metabolic capacity could be important determinants of bioavailability in serum and tissues. Ginsenosides and their aglycones, mainly 20(S)-protopanaxadiol (aPPD) and 20(S)-protopanaxatriol (aPPT), are routinely ingested as health supplements. The purpose of the present study was to investigate the potential of ginsenosides and their aglycones to block hepatic and intestinal inactivation of 1α,25(OH)2D3, which is the most potent ligand of vitamin D receptor. In vitro biotransformation reactions were initiated with NADPH regenerating solutions following initial preincubation of pooled human hepatic or intestinal microsomal protein or human recombinant CYP3A4 supersomes with 1α,25(OH)2D3 or midazolam. Formation of hydroxylated metabolites of 1α,25(OH)2D3 or midazolam was analyzed using liquid chromatography-mass spectrometry. Co-incubation of 1α,25(OH)2D3 with various ginsenosides (Rg1, Rh2, aPPD, aPPT and total ginsenosides) led to differential inhibition (30-100%) of its hydroxylation. Results suggest that aPPD, aPPT and Rh2 strongly attenuated the hydroxylation of 1α,25(OH)2D3. Follow up inhibition studies with aPPD and aPPT at varying concentrations (0.5-100µM) led to up to 91-100% inhibition of formation of hydroxylated metabolites of 1α,25(OH)2D3 thus preventing inactivation of active vitamin D3. The IC50 values of aPPD or aPPT for the most abundant hydroxylated metabolites of 1α,25(OH)2D3 ranged from 3.3 to 9.0µM in human microsomes. The inhibitory mechanism of aPPD or aPPT for CYP3A4-mediated biotransformation of 1α,25(OH)2D3 was competitive in nature (apparent Ki: 1.7-2.9µM). Similar inhibitory effects were also observed upon addition of aPPD or aPPT into midazolam hydroxylation assay. In summary, our results suggest that ginsenosides, specifically aPPD and aPPT, inhibit the CYP3A4-mediated catabolism of active vitamin D3 in human liver and intestine, potentially providing additional vitamin D-related benefits to patients with cancer, neurodegenerative and metabolic diseases.

Abiraterone inhibits 1α,25-dihydroxyvitamin D3 metabolism by CYP3A4 in human liver and intestine in vitro.

The chemopreventive and therapeutic effects of vitamin D3 are exerted through its dihydroxylated metabolite, 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3]. Inactivation of 1α,25(OH)2D3 by cytochrome P450 3A4 (CYP3A4) may be an important determinant of its serum and tissue levels. Abiraterone, a steroidogenesis inhibitor used in late stage prostate cancer treatment, is a CYP17A1 inhibitor. The purpose of this study was to assess the potential of abiraterone to block hepatic and intestinal inactivation of biologically active vitamin D3in vitro and to evaluate if abiraterone can alter CYP3A4 marker substrate activities. Biotransformation reactions were initiated with NADPH regenerating solutions following initial preincubation of pooled human hepatic or intestinal microsomal protein or human recombinant CYP3A4 supersomes with 1α,25(OH)2D3, midazolam or triazolam for 10min at 37°C. Formation of hydroxylated metabolites of 1α,25(OH)2D3, midazolam or triazolam was analyzed by liquid chromatography-mass spectrometry method. Co-incubation of 1α,25(OH)2D3 with abiraterone at varying concentrations (0.2-100µM) led to up to ∼85% inhibition of formation of hydroxylated metabolites of 1α,25(OH)2D3 thus preventing inactivation of active vitamin D3. The IC50 values for individual metabolites of 1α,25(OH)2D3 ranged from 0.4 to 2.2µM in human liver microsomes or human intestinal microsomes. The mechanism of CYP3A4-mediated inhibition of 1α,25(OH)2D3 by abiraterone was competitive (apparent Ki 2.8-4.3µM). Similar inhibitory effects were also observed upon inclusion of abiraterone into midazolam or triazolam hydroxylation assays. In summary, our results suggest that abiraterone inhibits the CYP3A4-mediated inactivation of active vitamin D3 in human liver and intestine, potentially providing additional anti-cancer benefits to prostate cancer patients. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Cytochrome P450 3A-mediated microsomal biotransformation of 1α,25-dihydroxyvitamin D3 in mouse and human liver: drug-related induction and inhibition of catabolism.

The biological activities of vitamin D(3) are exerted through the dihydroxy metabolite of vitamin D(3) [1α,25(OH)(2)D(3)]. Hepatic biotransformation of 1α,25(OH)(2)D(3) by cytochrome P450 (P450) enzymes could be an important determinant of bioavailability in serum and tissues. In the present study, we investigated the comparative biotransformation of 1α,25(OH)(2)D(3) in mouse and human liver microsomes and determined the effects of commonly used drugs on the catabolism of 1α,25(OH)(2)D(3). Severe symptoms of vitamin D deficiency have historically been observed in patients who received dexamethasone. To compare the effects of clinically important glucocorticoids with hepatic biotransformation of 1α,25(OH)(2)D(3), adult male CD-1 mice were given intraperitoneal injections of either vehicle (50% ethanol), dexamethasone (80 mg/kg per day), or prednisone (80 mg/kg per day) for three consecutive days. Hydroxy metabolite formation pattern and the extent of substrate depletion were similar in mouse liver microsomes (MLM) from vehicle- or prednisone-treated mice, whereas treatment with dexamethasone led to the emergence of additional metabolites and increased substrate depletion, as determined by liquid chromatography/mass spectrometry. The metabolite formation profile in vehicle-treated mice was different from that of human liver microsomes (HLM). Selective P450 chemical inhibitors have demonstrated that CYP3A isoforms are responsible for the microsomal biotransformation of 1α,25(OH)(2)D(3) in MLM. Coincubation of 1α,25(OH)(2)D(3) with commonly used drugs led to approximately 60 to 100% inhibition of CYP3A4-mediated catabolism of 1α,25-(OH)(2)D(3) in HLM. A species-based difference was identified between CYP3A-mediated hepatic microsomal metabolism of 1α,25(OH)(2)D(3) in humans and mice. We have shown that the clinical importance of glucocorticoids differentially modulates catabolism of active vitamin D(3) and that commonly used drugs could affect vitamin D homeostasis.

Fluorescent adducts formed by reaction of oxidized unsaturated fatty acids with amines increase macrophage viability.

Macrophages are prominent components of human atherosclerotic lesions and they are believed to accelerate the progression and/or complications of both early and advanced atherosclerotic lesions. We and others have shown that oxidized low-density lipoprotein (oxLDL) induces growth and inhibits apoptosis in murine bone marrow-derived macrophages. In this study, we sought to characterize the oxidative modification of LDL that is responsible for this prosurvival effect. We found that both the modified lipid and the modified protein components of oxLDL can increase the viability of macrophages. The key modification appeared to involve derivatization of amino groups in apoB or in phosphatidylethanolamine by lipid peroxidation products. These reactive oxidation products were primarily unfragmented hydroperoxide- or endoperoxide-containing oxidation products of linoleic acid or arachidonic acid. LC-MS/MS studies showed that some of the arachidonic acid-derived lysine adducts were isolevuglandins that contain lactam and hydroxylactam rings. MS/MS analysis of linoleic acid autoxidation adducts was consistent with 5- or 6-membered nitrogen-containing heterocycles derived from unfragmented oxidation products. The amine modification by oxidation products generated a fluorescence pattern with an excitation maximum at 350nm and emission maximum at 430nm. This is very similar to the fluorescence spectrum of copper-oxidized LDL.

Inhibitors of androgen receptor activation function-2 (AF2) site identified through virtual screening.

The androgen receptor (AR) is one of the most studied drug targets for the treatment of prostate cancer. However, all current anti-androgens directly interact with the AR at the androgen binding site, which is prone to resistant mutations, calling for new strategies of the AR inhibition. The current study represents the first attempt to use virtual screening to identify inhibitors of activation function-2 (AF2) of the human AR. By combining large-scale docking with experimental approaches, we were able to identify several small molecules that interact with the AF2 and effectively prevent the transcriptional activation of the AR. The crystallographic structure of one of these inhibitors in complex with the AR provides critical insight into the corresponding protein-ligand interactions and suitable for future hit optimization. Taken together, our results provide a promising ground for development of novel anti-androgens that can help to address the problem of drug resistance in prostate cancer.

Arachidonic acid activation of intratumoral steroid synthesis during prostate cancer progression to castration resistance.

BACKGROUND: De novo androgen synthesis and subsequent androgen receptor (AR) activation has recently been shown to contribute to castration-resistant prostate cancer (CRPC) progression. Herein we provide evidence that fatty acids (FA) can trigger androgen synthesis within steroid starved prostate cancer (CaP) tumor cells. METHODS: Tumoral FA and steroid levels were assessed by GC-MS and LC-MS, respectively. Profiles of genes and proteins involved in FA activation of steroidogenesis were assessed by fluorescence microscopy, immunohistochemistry, microarray expression profiling and Western blot analysis. RESULTS: In human CaP tissues the levels of proteins responsible for FA activation of steroid synthesis were observed to be altered during progression to CRPC. Further investigating this mechanism in LNCaP cells, we demonstrate that specific FA, arachidonic acid, is synthesized in an androgen-dependent and AR-mediated manner. Arachidonic acid is known to induce steroidogenic acute regulatory protein (StAR) in steroidogenic cells. When bound to hormone sensitive lipase (HSL), StAR shuttles free cholesterol into the mitochondria for downstream conversion into androgens. We show that arachidonic acid induces androgen production in steroid starved LNCaP cells coincidently in the same conditions that HSL and StAR are predominantly localized in the mitochondria. Furthermore, their activities are verified by a functional increase in mitochondrial uptake of cholesterol in this steroid starved environment. CONCLUSIONS: We propose that this characterized arachidonic acid induced steroidogenesis mechanism significantly contributes to the activation of AR in CRPC progression and therefore recommend that fatty acid pathways be targeted therapeutically in progressing CaP.

Steroidogenesis inhibitors alter but do not eliminate androgen synthesis mechanisms during progression to castration-resistance in LNCaP prostate xenografts.

In castration-resistant prostate cancer (CRPC) many androgen-regulated genes become re-expressed and tissue androgen levels increase despite low serum levels. We and others have recently reported that CRPC tumor cells can de novo synthesize androgens from adrenal steroid precursors or cholesterol and that high levels of progesterone exist in LNCaP tumors after castration serving perhaps as an intermediate in androgen synthesis. Herein, we compare androgen synthesis from [(3)H-progesterone] in the presence of specific steroidogenesis inhibitors and anti-androgens in steroid starved LNCaP cells and CRPC tumors. Similarly, we compare steroid profiles in LNCaP tumors at different stages of CRPC progression. Steroidogenesis inhibitors targeting CYP17A1 and SRD5A2 significantly altered but did not eliminate androgen synthesis from progesterone in steroid starved LNCaP cells and CRPC tumors. Upon exposure to inhibitors of steroidogenesis prostate cancer cells adapt gradually during CRPC progression to synthesize DHT in a compensatory manner through alternative feed-forward mechanisms. Furthermore, tumors obtained immediately after castration are significantly less efficient at metabolizing progesterone ( approximately 36%) and produce a different steroid profile to CRPC tumors. Optimal targeting of the androgen axis may be most effective when tumors are least efficient at synthesizing androgens. Confirmatory studies in humans are required to validate these findings.