Castration-recurrent Prostate Cancer Research Articles

Abstract 4900: MAGE-A11 expression in castration-recurrent prostate cancer: association with a global epigenetic defect

Abstract Despite the initial clinical response to androgen deprivation therapy, most prostate cancer patients subsequently develop castration-recurrent disease. Elucidation of the mechanisms driving this process is expected to lead to improved strategies to prevent and treat advanced prostate cancer. Epigenetic alterations, including DNA hypomethylation, play a key role in human cancer development. DNA hypomethylation is thought to promote oncogenesis in part by driving oncogene expression, but its potential role in castration-recurrent prostate cancer is unknown. Melanoma Antigen A-11 (MAGE-A11) is a cancer germline (CG) antigen that stabilizes the androgen receptor (AR), facilitates AR association with co-activators, and promotes AR transcriptional activity; thus it appears to play an oncogenic role in castration-recurrent disease. We have recently reported that MAGE-A11 is over-expressed in prostate cancer cell lines, prostate cancer xenografts, and human prostate cancer tissues; in each setting MAGE-A11 overexpression is associated with DNA hypomethylation at the MAGE-A11 promoter CpG island (Karpf et al., Molecular Cancer Research 7; 523-535, 2009). Critically, MAGE-A11 expression and promoter hypomethylation correlate with castration-recurrent cancer growth, both in the CWR-22 xenograft model and in primary human prostate cancer tissues. In the current study we examined whether MAGE-A11 expression and hypomethylation in prostate cancer is an isolated molecular event, or alternatively whether it coincides with a global DNA hypomethylation defect. To test this, we analyzed the global DNA methylation status of prostate cancer cell lines, CWR-22 cancer xenografts, and primary prostate cancer, in which MAGE-A11 expression and methylation was also characterized. We assessed global DNA methylation by measuring total genomic 5-methyl-2′-deoxycytidine (5mdC), LINE-1 repetitive DNA element methylation, and the expression and methylation of several other CG antigen genes, including MAGE-A1, NY-ESO-1, XAGE-1, and BORIS/CTCFL. Taken together, our data provide evidence for a global DNA hypomethylation phenotype in castration-recurrent prostate cancers that express MAGE-A11. Ongoing studies are using HpaII tiny fragment enrichment by ligation-mediated PCR (HELP assay) to define the epigenome of castration-recurrent prostate cancer displaying MAGE-A11 expression. In summary, our data provide evidence that global DNA hypomethylation contributes to castration-recurrent prostate cancer, at least in part by promoting MAGE-A11 expression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4900.

14-3-3η Amplifies Androgen Receptor Actions in Prostate Cancer

PURPOSE: Androgen receptor abundance and androgen receptor-regulated gene expression in castration-recurrent prostate cancer are indicative of androgen receptor activation in the absence of testicular androgen. Androgen receptor transactivation of target genes in castration-recurrent prostate cancer occurs in part through mitogen signaling that amplifies the actions of androgen receptor and its coregulators. Herein we report on the role of 14-3-3eta in androgen receptor action. Experimental Design and RESULTS: Androgen receptor and 14-3-3eta colocalized in COS cell nuclei with and without androgen, and 14-3-3eta promoted androgen receptor nuclear localization in the absence of androgen. 14-3-3eta interacted with androgen receptor in cell-free binding and coimmunoprecipitation assays. In the recurrent human prostate cancer cell line, CWR-R1, native endogenous androgen receptor transcriptional activation was stimulated by 14-3-3eta at low dihydrotestosterone concentrations and was increased by epidermal growth factor. Moreover, the dihydrotestosterone- and epidermal growth factor-dependent increase in androgen receptor transactivation was inhibited by a dominant negative 14-3-3eta. In the CWR22 prostate cancer xenograft model, 14-3-3eta expression was increased by androgen, suggesting a feed-forward mechanism that potentiates both 14-3-3eta and androgen receptor actions. 14-3-3eta mRNA and protein decreased following castration of tumor-bearing mice and increased in tumors of castrate mice after treatment with testosterone. CWR22 tumors that recurred 5 months after castration contained 14-3-3eta levels similar to the androgen-stimulated tumors removed before castration. In a human prostate tissue microarray of clinical specimens, 14-3-3eta localized with androgen receptor in nuclei, and the similar amounts expressed in castration-recurrent prostate cancer, androgen-stimulated prostate cancer, and benign prostatic hyperplasia were consistent with androgen receptor activation in recurrent prostate cancer. CONCLUSION: 14-3-3eta enhances androgen- and mitogen-induced androgen receptor transcriptional activity in castration-recurrent prostate cancer. (Clin Cancer Res 2009;15(24):7571-81).

Androgen receptor abnormalities in castration-recurrent prostate cancer

The androgen receptor (AR) plays a critical role in prostate cancer (PCa) development and progression. Despite the success of androgen-deprivation therapy, remission occurs in almost all cases. This stage of the disease is called castration-recurrent PCa (CRPC). CRPC cells adapt to low circulating levels of androgens, and active AR is maintained by numerous cellular mechanisms. Some mutations in the AR make it more responsive to lower androgen levels or other steroids. Furthermore, in this advance stage of the disease, PCa cells express the enzymes necessary for de novo synthesis of androgens. AR is also activated in a ligand-independent manner. Therefore, it is important to understand the mechanisms of AR activation and its deregulation during CRPC. The purpose of this article is to discuss mechanisms that are involved in modulation of AR activity and specificity.

Increased Expression of Androgen Receptor Coregulator MAGE-11 in Prostate Cancer by DNA Hypomethylation and Cyclic AMP

Melanoma antigen gene protein-A11 (MAGE-11) of the MAGE family of cancer germ-line antigens increases androgen receptor (AR) transcriptional activity through its interaction with the AR NH(2)-terminal FXXLF motif. The present study investigated the regulatory mechanisms that control MAGE-11 expression during androgen deprivation therapy and prostate cancer progression. Studies include the CWR22 xenograft model of human prostate cancer, clinical specimens of benign and malignant prostate, and prostate cancer cell lines. MAGE-11 mRNA levels increased 100- to 1,500-fold during androgen deprivation therapy and prostate cancer progression, with highest levels in the castration-recurrent CWR22 xenograft and clinical specimens of castration-recurrent prostate cancer. Pyrosequencing of genomic DNA from prostate cancer specimens and cell lines indicated the increase in MAGE-11 resulted from DNA hypomethylation of a CpG island in the 5' promoter of the MAGE-11 gene. Sodium bisulfite sequencing of genomic DNA from benign and malignant prostate tumors and prostate cancer cell lines revealed DNA hypomethylation at individual CpG sites at the transcription start site were most critical for MAGE-11 expression. Cyclic AMP (cAMP) also increased MAGE-11 expression and AR transcriptional activity in prostate cancer cell lines. However, cAMP did not alter DNA methylation of the promoter and its effects were inhibited by extensive DNA methylation in the MAGE-11 promoter region. Increased expression of the AR coregulator MAGE-11 through promoter DNA hypomethylation and cAMP provides a novel mechanism for increased AR signaling in castration-recurrent prostate cancer.

Androgen Modulation of Coregulator Expression in Prostate Cancer Cells

Aberrant coregulator expression that occurs during prostate cancer (PCa) progression correlates with poor prognosis and aggressive disease. This has been attributed to the ability to regulate androgen receptor-mediated transcription. We have shown previously that the androgenic milieu regulates the expression of the coactivators p300 and FHL2, with severe consequences for PCa cell proliferation and androgen receptor transcriptional activity. To determine the extent of androgen dependency of coregulator genes, we designed a cDNA-mediated annealing, selection, extension, and ligation RNA profiling array that probes the expression of 186 coregulators. Using this assay, we demonstrated androgen control over approximately 30% of coregulator genes in PCa cells. For a subset of 15 functionally diverse coregulators, androgen regulation was confirmed using real-time RT-PCR and immunoblotting. The extent, dose dependency, and kinetics by which androgens affect coregulator expression differed widely, indicating diverse molecular mechanisms underlying these effects. Moreover, differences in coregulator expression were observed between isogenic androgen-dependent and castration-recurrent PCa cells. Small interfering RNA-mediated changes in coregulator expression had profound effects on cell proliferation, which were most pronounced in castration-recurrent cells. Taken together, our integrated approach combining expression profiling, characterization of androgen-dependent coregulator expression, and validation of the importance of altered coregulator expression for cell proliferation identified several potential novel therapeutic targets for PCa treatment.

Overexpression of 5α‐reductase type 1 increases sensitivity of prostate cancer cells to low concentrations of testosterone

Conversion of testosterone to dihydrotestosterone (DHT) by the enzymes 5 alpha-reductase types 1 (5 alpha R1) and 2 (5 alpha R2) is important for normal and pathological growth of the prostate. The predominant isoenzyme in normal prostate is 5 alpha R2. However, prostate cancer (PCa) development is accompanied by a decrease in 5 alpha R2 and an increase in 5 alpha R1. The biological significance of increased 5 alpha R1 expression is not fully understood. Therefore, the aim of this study was to determine the effect of overexpression of 5 alpha R1 on growth and prostate-specific antigen (PSA) production in PCa cells. LNGK-9 PCa cells, transiently transfected with pTRE-5 alpha R1 or pTRE alone, were cultured in the presence or absence of testosterone at varying concentrations. Cell growth and PSA secretion were measured after 4-6 days. Cyclin E1, Ki67, and PSA mRNA levels were evaluated using RT-PCR after 24 hr of treatment. 10 pM testosterone increased growth of pTRE-5 alpha R1 transfectants by 54.1% over cells grown in the absence of testosterone, compared to 25.0% in pTRE transfectants (P < 0.01). Likewise, PSA secretion was increased by 56-fold in pTRE-5 alpha R1 transfectants treated with 10 pM testosterone, compared to 26-fold in pTRE transfectants (P < 0.01). At concentrations of testosterone above 10 pM, the stimulatory effect on growth and PSA secretion was not distinguishable between pTRE-5 alpha R1 and pTRE transfectants. These results demonstrate that upregulation of 5 alpha R1 enhances the cellular response to low, but not high, concentrations of testosterone. This explains one mechanism by which castration-recurrent PCa can proliferate in the presence of castrate levels of circulating testosterone.

Phase II Study of Dutasteride for Recurrent Prostate Cancer During Androgen Deprivation Therapy

We determined the response rate to and safety of a dual 5alpha-reductase inhibitor, dutasteride, in men with castration recurrent prostate cancer. A total of 28 men with asymptomatic castration recurrent prostate cancer were treated with 3.5 mg dutasteride daily (luteinizing hormone-releasing hormone treatment continued), and evaluated monthly for response and toxicity. Eligibility included appropriate duration antiandrogen withdrawal, baseline prostate specific antigen 2.0 ng/ml or greater and a new lesion on bone scan, increase in measurable disease using Response Evaluation Criteria in Solid Tumors criteria, or 2 or more consecutive prostate specific antigen measurements increased over baseline. Outcomes were progression, stable disease, partial response (prostate specific antigen less than 50% of enrollment for 4 or more weeks) or complete response. There were 25 evaluable men with a mean age of 70 years (range 57 to 88), a mean prostate specific antigen of 61.9 ng/ml (range 5.0 to 488.9) and mean Gleason score 8 (range 6 to 10), 15 of whom had bone metastases. Eight men had 10 grade 3 or higher adverse events using National Cancer Institute Common Terminology Criteria, all of which were judged to be unrelated to treatment. Of the 25 men 14 had disease progression by 2 months, 9 had stable (2.5, 3, 3, 4, 4, 5, 5, 8.5, 9 months) disease, 2 had a partial response and none had a complete response. Overall median time to progression was 1.87 months (range 1 to 10, 95% CI 1.15-3.91). Dutasteride rarely produces biochemical responses in men with castration recurrent prostate cancer. However, further study is warranted given its favorable safety profile.

Site-specific Androgen Receptor Serine Phosphorylation Linked to Epidermal Growth Factor-dependent Growth of Castration-recurrent Prostate Cancer

The androgen receptor (AR) is required for prostate cancer development and contributes to tumor progression after remission in response to androgen deprivation therapy. Epidermal growth factor (EGF) increases AR transcriptional activity at low levels of androgen in the CWR-R1 prostate cancer cell line derived from the castration-recurrent CWR22 prostate cancer xenograft. Here we report that knockdown of AR decreases EGF stimulation of prostate cancer cell growth and demonstrate a mechanistic link between EGF and AR signaling. The EGF-induced increase in AR transcriptional activity is dependent on phosphorylation at mitogen-activated protein kinase consensus site Ser-515 in the AR NH(2)-terminal region and at protein kinase C consensus site Ser-578 in the AR DNA binding domain. Phosphorylation at these sites alters the nuclear-cytoplasmic shuttling of AR and AR interaction with the Ku-70/80 regulatory subunits of DNA-dependent protein kinase. Abolishing AR Ser-578 phosphorylation by introducing an S578A mutation eliminates the AR transcriptional response to EGF and increases both AR binding of Ku-70/80 and nuclear retention of AR in association with hyperphosphorylation of AR Ser-515. The results support a model in which AR transcriptional activity increases castration-recurrent prostate cancer cell growth in response to EGF by site-specific serine phosphorylation that regulates nuclear-cytoplasmic shuttling through interactions with the Ku-70/80 regulatory complex.

Inverse correlation between body mass index and clinical outcomes in men with advanced castration–recurrent prostate cancer

Obesity has a variety of adverse health outcomes, but to the authors' knowledge, the effect of obesity on outcome in patients with advanced prostate cancer is not known. For this reason, the correlation between an elevated body mass index (BMI) and clinical outcomes in patients with metastatic, castration-recurrent prostate cancer (CRPC) was evaluated. A total of 1226 men with CRPC who were enrolled in 9 prospective clinical trials conducted by the Cancer and Leukemia Group B (CALGB) for the treatment of metastatic disease were considered. Eligible patients had progressive prostate cancer during androgen deprivation therapy (with documented castrate levels of testosterone); an Eastern Cooperative Oncology Group performance status of 0 to 2; and adequate hematologic, renal, and hepatic function. Patients were classified based on BMI as normal (18.5-24.9 kg/m(2)), overweight (25-29.9 kg/m(2)), and mildly to severely obese (> or =30 kg/m(2)). Approximately 24% of the patients had a normal BMI, 43% were overweight, and 33% were mildly to severely obese. On multivariable analysis, BMI was found to be a statistically significant predictor of overall survival and prostate cancer-specific mortality. Compared with men with normal BMIs, the hazard ratios for death for overweight men and mildly to severely obese men were 0.80 (95% confidence interval [95% CI], 0.68-0.93; P = .001) and 0.80 (95% CI, 0.68-0.94; P = .010), respectively. In patients with metastatic CRPC, obesity (as defined by an elevated BMI) appears to have a protective effect against overall mortality and prostate cancer-specific mortality. Alternatively, a higher BMI may reflect different cancer biology (ie, the lack of cachexia-producing substances). Further studies to gain a more comprehensive understanding of the mechanisms behind these clinical observations are needed.

A novel intermediate endpoint for predicting overall survival in men with metastatic castration-recurrent prostate cancer (CRPC)

5113 Background: In this proposed study, we developed and validated a novel composite clinical benefit endpoint constructed from symptoms that have intrinsic clinical importance in 800 men with CRPC who were treated with front-line chemotherapy. Methods: Data from nine multimember trials (five phase II and four randomized phase III studies) conducted by the Cancer and Leukemia Group B (CALGB) from 1992–2004 were combined. Eligible patients had progressive adenocarcinoma of the prostate during androgen ablation (despite castrate testosterone levels), an ECOG performance status of 0–2, adequate hematologic, renal and hepatic functions. The tripartite composite clinical benefit endpoint (TCCBE) had three components: one based on disease progression (whether it be PSA, bone, or soft tissue progression), and the second based on weight loss (defined as at least 10% decline from baseline) or on performance status (PS) decline (by at least one level) to capture clinical deterioration. The third component was based on pain control and opioid analgesic use (no or yes). For a person to fall in the TCCBE “yes” category, at least two of the three components had to be recorded as no. For instance, if a patient at 3 months had no progression, no change in weight and did not use opioid analgesic, then he will be classified in the “yes” group and for the purpose of this analysis was considered as someone who achieved “clinical benefit”. The sample was randomly split into 526 (67%) and 274 (33%) men in the training and testing datasets, respectively. Results: From the training dataset, the median survival times in men who had and did not have clinical benefit were 20.9 months (95% confidence interval (CI) = 18.5–22.8) and 11.1 months (95% = 8.79–12.6, p- value&lt;0.001). In the testing dataset, the median survival times in men with and without clinical benefit were 21.7 months (95% CI= 19.1–26.1) and 8.8 months (95% CI= 7.8–11.6) and in men. The hazard ratio (HR) for men with a clinical benefit compared to men without was 0.52 (95% CI= 0.43–0.62, P&lt;0.001). Conclusions: The TCCBE is a statistically significant intermediate endpoint for predicting overall survival. Prospective validation of this endpoint is needed. No significant financial relationships to disclose.

The Impact of Prior Radical Prostatectomy in Men With Metastatic Castration Recurrent Prostate Cancer: A Pooled Analysis of 9 Cancer and Leukemia Group B Trials

A prior report suggested that radical prostatectomy may confer a survival advantage to patients with metastatic castration recurrent prostate cancer. Therefore, a pooled analysis of 9 trials performed by Cancer and Leukemia Group B was done to determine if men with metastatic castration recurrent prostate cancer who underwent prior prostatectomy had improved clinical outcomes, such as overall, prostate specific, progression-free and PSA progression-free survival, than men who did not undergo prior prostatectomy. Data from 9 multi-institutional trials performed by Cancer and Leukemia Group B were combined. Eligible patients had progressive prostate cancer during androgen deprivation therapy, Eastern Cooperative Oncology Group performance status 0-2, and adequate hematological, renal and hepatic functions. The proportional hazards model was used to assess the prognostic importance of radical prostatectomy for predicting clinical outcomes. Of 1,238 men 310 (25%) underwent prostatectomy. Median survival was 14.7 (95% CI 12.9-16.7) and 14.5 months (95% CI 13.5-15.7) in men who did and did not undergo prostatectomy, respectively. The HR for death was 1.03 (95% CI 0.90-1.19, p = 0.65) in men with vs without prostatectomy. Prior prostatectomy in men with metastatic castration recurrent prostate cancer who were subsequently enrolled on clinical trials for cancer treatment had similar survival compared to men who did not undergo prior prostatectomy. These data do not support another report suggesting that prior prostatectomy confers a subsequent survival advantage in men with castration recurrent prostate cancer.

MP-22.11: Phase II clinical trial of dutasteride in castration-recurrent prostate cancer

MP-22.11: Phase II clinical trial of dutasteride in castration-recurrent prostate cancer