Trials In Castration-resistant Prostate Cancer Research Articles

Computational drug discovery for castration-resistant prostate cancers through in vitro drug response modeling

Prostate cancer (PC) is the most frequently diagnosed malignancy and a leading cause of cancer deaths in US men. Many PC cases metastasize and develop resistance to systemic hormonal therapy, a stage known as castration-resistant prostate cancer (CRPC). Therefore, there is an urgent need to develop effective therapeutic strategies for CRPC. Traditional drug discovery pipelines require significant time and capital input, which highlights a need for novel methods to evaluate the repositioning potential of existing drugs. Here, we present a computational framework to predict drug sensitivities of clinical CRPC tumors to various existing compounds and identify treatment options with high potential for clinical impact. We applied this method to a CRPC patient cohort and nominated drugs to combat resistance to hormonal therapies including abiraterone and enzalutamide. The utility of this method was demonstrated by nomination of multiple drugs that are currently undergoing clinical trials for CRPC. Additionally, this method identified the tetracycline derivative COL-3, for which we validated higher efficacy in an isogenic cell line model of enzalutamide-resistant vs. enzalutamide-sensitive CRPC. In enzalutamide-resistant CRPC cells, COL-3 displayed higher activity for inhibiting cell growth and migration, and for inducing G1-phase cell cycle arrest and apoptosis. Collectively, these findings demonstrate the utility of a computational framework for independent validation of drugs being tested in CRPC clinical trials, and for nominating drugs with enhanced biological activity in models of enzalutamide-resistant CRPC. The efficiency of this method relative to traditional drug development approaches indicates a high potential for accelerating drug development for CRPC.

Local Therapy for Oligoprogressive Disease: A Systematic Review of Prospective Trials

The successes of local therapy for oligometastatic cancers cannot be extrapolated to oligoprogressive disease (OPD) because they are distinct clinical entities. Given the limited prospective data on OPD to date, summative analyses are urgently needed. Inclusion criteria for this Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-guided systematic review were as follows. First, only prospective data were included. Second, progression had to have occurred on active/ongoing systemic therapy. Third, the number of progressing areas of disease had to be explicitly listed and ≤5 in number. Fourth, all progressing sites had to undergo local therapy (radiation therapy [RT] /surgery/nonradiation ablative procedures). Eight trials met criteria (summing 290 patients), the vast majority of which used stereotactic RT as the local modality (most commonly, 19-20 Gy in 1 fraction, 27-33 Gy in 3 fractions, or 35-50 Gy in 5 fractions). A study on non-small cell lung cancer (NSCLC) demonstrated that stereotactic RT improved progression-free survival (PFS) and overall survival compared with historical values with systemic therapy alone. Two additional studies on epidermal growth factor receptor mutated (EGFRm) NSCLC also showed acceptable PFS with local therapy, particularly in patients who oligoprogressed on osimertinib. The only randomized trial analyzed herein showed that local therapy improved PFS for NSCLC but not breast cancer. Two trials in castration-resistant prostate cancer illustrated that a substantial proportion of patients did not require any changes in hormonal therapy or delayed the need to change systemic therapies. Lastly, 2 trials of renal cell carcinoma showed high (90%-100%) local control and median PFS of 9 months, and potentially a prolonged time to change systemic therapy. Lastly, from all patients in all trials, local therapy was tolerated well, with only 7 instances of grade 3+ toxicities. Based on the limited data, local therapy for oligoprogression is safe and yields encouraging short-term preliminary outcomes, but trials with larger sample sizes and longer follow-up are required for more robust conclusions.

Exploiting the tumor-suppressive activity of the androgen receptor by CDK4/6 inhibition in castration-resistant prostate cancer

The androgen receptor (AR) plays a pivotal role in driving prostate cancer (PCa) development. However, when stimulated by high levels of androgens, AR can also function as a tumor suppressor in PCa cells. While the high-dose testosterone (high-T) treatment is currently being tested in clinical trials of castration-resistant prostate cancer (CRPC), there is still a pressing need to fully understand the underlying mechanism and thus develop treatment strategies to exploit this tumor-suppressive activity of AR. In this study, we demonstrate that retinoblastoma (Rb) family proteins play a central role in maintaining the global chromatin binding and transcriptional repression program of AR and that Rb inactivation desensitizes CRPC to the high-dose testosterone treatment invitro and invivo. Using a series of patient-derived xenograft (PDX) CRPC models, we further show that the efficacy of high-T treatment can be fully exploited by a CDK4/6 inhibitor, which strengthens the chromatin binding of the Rb-E2F repressor complex by blocking the hyperphosphorylation of Rb proteins. Overall, our study provides strong mechanistic and preclinical evidence on further developing clinical trials to combine high-T with CDK4/6 inhibitors in treating CRPC.

Improving power in PSA response analyses of metastatic castration-resistant prostate cancer trials

BackgroundTo determine how much an augmented analysis approach could improve the efficiency of prostate-specific antigen (PSA) response analyses in clinical practice. PSA response rates are commonly used outcome measures in metastatic castration-resistant prostate cancer (mCRPC) trial reports. PSA response is evaluated by comparing continuous PSA data (e.g., change from baseline) to a threshold (e.g., 50% reduction). Consequently, information in the continuous data is discarded. Recent papers have proposed an augmented approach that retains the conventional response rate, but employs the continuous data to improve precision of estimation.MethodsA literature review identified published prostate cancer trials that included a waterfall plot of continuous PSA data. This continuous data was extracted to enable the conventional and augmented approaches to be compared.ResultsSixty-four articles, reporting results for 78 mCRPC treatment arms, were re-analysed. The median efficiency gain from using the augmented analysis, in terms of the implied increase to the sample size of the original study, was 103.2% (IQR [89.8,190.9%]).ConclusionsAugmented PSA response analysis requires no additional data to be collected and can be performed easily using available software. It improves precision of estimation to a degree that is equivalent to a substantial sample size increase. The implication of this work is that prostate cancer trials using PSA response as a primary endpoint could be delivered with fewer participants and, therefore, more rapidly with reduced cost.

Abstract LB-A13: LSD1 activates both PI3K/AKT and AR signaling in prostate cancer cells

Abstract Background: Lysine specific demethylase 1 (LSD1/KDM1A), a specific demethylase of mono- or di-methylated histone lysine 4 (H3K4me1,2, enhancer-associated signature), was first identified as a component of REST repressor complex composed of CoREST and histone deacetylases 1, 2 (HDAC1,2). In hematopoietic malignancies, targeting LSD1 has shown very promising clinical outcomes, potentially through promoting myeloid differentiation. In solid tumors, multiple mechanisms have been proposed for the antitumor effect of inhibiting LSD1. While LSD1 is well known for its transcription repressor activity, it also activates gene transcription through demethylating repressive histone marks, such as H3K9me1,2, and possibly other non-histone proteins. In particular, LSD1 functions as a major androgen receptor (AR) coactivator in prostate cancer (PCa) cells. Indeed, we reported that LSD1 interacts and colocalizes with FOXA1, a pioneer factor of AR, at AR-mediated enhancers, and this interaction may facilitate AR transcription activity. Nonetheless, since AR signaling is critical to PCa development and progression to the lethal stage of castration-resistant PCa (CRPC), studies from us and others highly suggest that targeting LSD1 may be a potential treatment strategy for CRPC, where AR signaling is commonly restored. However, whether LSD1 regulates other major tumor-promoting pathways in PCa cells remains to be determined. Identification of suchcritical LSD1 targets will provide important insights for developing more effective therapeutic strategy for treating PCa. Experiments and Results: To address this question, we conducted RNA-seq analyses of LSD1 inhibitor treated PCa cells. We first confirmed that prolonged LSD1 inhibitor treatment in the presence of androgens broadly impaired AR transcriptional output. Importantly, we found that the LSD1 inhibitor repressed genes were also enriched for PI3K/AKT pathway even in absence of androgen stimulation. We further confirmed that LSD1 inhibition and Knock-out significantly decreased AKT phosphorylation, which interestingly is independent of AR signaling, as targeting LSD1 also decreased AKT phosphorylation in AR negative PCa cells. Through functional annotation analyses and subsequent validations, we identified the regulatory subunit of PI3K, p85α and possibly its isoform p85β, as a critical transcriptional target of LSD1 that mediates its effect on PI3K/AKT pathway activation. Using a combined analysis with ChIP-seq against LSD1 and H3K4me2, we identified a regulatory region on the PIK3R1 gene loci that may be responsible for regulating its gene transcription. We further investigated the effect of LSD1 inhibitor treatment in LuCaP35CR, a patient-derived CRPC xenograft model which is TMPRSS2-ERG positive and PTEN-negative. Using this model, we found that targeting LSD1 impaired the tumor growth and suppressed PI3K/AKT signaling. Conclusion: our study suggests that LSD1 has dual functions in promoting PCa development: 1) it enhances AR signaling through its coactivator function, 2) it activates PI3K/AKT signaling through increasing p85 gene expression. Based on these findings, it is plausible that the effectiveness of LSD1 inhibitor treatment in CRPC may be due to inhibition of both AR signaling and PI3K/AKT signaling pathways. As LSD1 inhibitors are currently being tested in phase II clinical trials of leukemia, our studies can be rapidly translated into clinical trials of CRPC. Citation Format: zifeng wang, Shuai Gao, Changmeng cai. LSD1 activates both PI3K/AKT and AR signaling in prostate cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr LB-A13. doi:10.1158/1535-7163.TARG-19-LB-A13

SAT-330 Preclinical Screen of Patient CRPC Tumors Shows Sensitivity to Bromodomain Inhibitors Includes AR-null and Neuroendocrine Disease

Castration-resistant prostate cancer (CRPC) remains a lethal disease despite the introduction of second generation androgen receptor (AR) directed therapies. Resistance to AR directed therapies, such as abiraterone and enzalutamide, emerges through diverse alterations in the AR pathway or transition to aggressive AR-null phenotypes. Although bromodomain and extra-terminal (BET) inhibitor therapies are in current clinical trials for CRPC, understanding of the full spectrum of patient responders is limited by a lack of models for preclincial testing. Thus, the goal of this study was to examine the efficacy of BET inhibitors in a panel of patient-derived models of CRPC, including AR-null and neuroendocrine differentiated tumors that are inherently resistant to AR-directed therapy. To rapidly screen the sensitivity of tumors to BET inhibitors, we used ex vivo cultures of patient-derived xenograft tissue from the MURAL (Melbourne Urological Research Alliance) cohort of patient tumors and treated them with JQ1. Changes in proliferation and apoptosis were measured using histology for Ki67 and cleaved caspase 3. Consistent with previous studies, our results showed that all AR-positive tumors were sensitive to JQ1, with decreases in proliferation and increases in apoptosis. Importantly, this includes tumors from patients who failed abiraterone and/or enzalutamide and have diverse alterations of the AR, including mutations, genomic amplifications and expression of truncated AR variants. Surprisingly, 50% of AR null tumors were just as sensitive to BET inhibitors and AR-positive tumors. This includes tumors with large cell and small cell neuroendocrine histopathology, which are inherently resistant to AR-directed therapies. We also assessed intra-patient heterogeneity by examining tumors from different metastases of the same patient. We observed consistent responses in one patient, but divergent responses in another, likely due to differences in AR status. Collectively, our data show that BET inhibitors are promising treatments for tumors with diverse mechanisms of resistance to AR-directed therapies; however, the responses of AR-null tumors are more heterogeneous. Therefore, further studies to identify biomarkers of responsiveness to BET inhibitors in AR-null and neuroendocrine tumors are warranted.

Adverse events of special interest assessed by review of safety data in enzalutamide castration-resistant prostate cancer (CRPC) trials.

237 Background: Androgen receptor inhibitor enzalutamide improves survival in patients with metastatic CRPC (mCRPC) and reduces risk of metastasis or death versus placebo in patients with non-metastatic CRPC (nmCRPC). This post hoc analysis evaluated the incidence of adverse events (AEs) of special interest reported with enzalutamide versus placebo in CRPC trials. Methods: Safety data from four Phase 3, placebo-controlled enzalutamide trials in men with CRPC (PROSPER, nmCRPC, NCT02003924; PREVAIL, mCRPC, NCT01212991; AFFIRM, mCRPC, NCT00974311; and 9785-CL-0232, mCRPC, NCT02294461) were assessed for AEs of special interest, including ischemic heart disease (IHD) [defined by narrow Standardised MedDRA Queries “Myocardial Infarction”/“Other Ischemic Heart Disease”], falls, and fractures. Data were reported as overall incidence and adjusted for treatment exposure (per 100 patient-years), and summarized as follows: patients receiving enzalutamide (n = 2799) and placebo (n = 1898) in all four Phase 3 trials. Results: Median treatment duration was 13.73 months with enzalutamide and 4.80 months with placebo in the combined Phase 3 trials. Overall incidence of IHD was higher with enzalutamide versus placebo in the combined Phase 3 trials (Table), remaining higher once adjusted for treatment exposure (2.5 with enzalutamide vs. 2.2 with placebo). Similarly, exposure-adjusted rate of falls and fractures were also higher with enzalutamide versus placebo (Table). Clinical trial information: NCT02003924 (PROSPER); NCT01212991 (PREVAIL); NCT00974311 (AFFIRM); NCT02294461 (9785-CL-0232). Conclusions: In this combined analysis of CRPC trials, incidences of IHD, falls, and fractures were higher with enzalutamide versus placebo in all patients. Efforts to identify patients at high risk for these AEs and reduce their risk, e.g. via exercise and cardiovascular risk reduction, are important in these patients, particularly in elderly men and those with cardiovascular comorbidities.[Table: see text]

849P - Quality of docetaxel toxicity reporting for castration resistant prostate cancer (CRPC): A systematic review

Background: Prostate cancer trial design is structured following the Prostate Cancer Clinical Trials Working Group (PCWG) guidelines which focus on harmonization of inclusion criteria and outcome data. The PCWG, however, does not provide clear outlines for reporting of safety data. In fact, there is a perceived lack of widely accepted guidelines for safety reporting. Methods: A PubMed search of phase II and III clinical trials published until 2015 (included) was conducted using keywords “prostate cancer” and “docetaxel.” Docetaxel-naïve CRPC patients who received 75 mg/m2 docetaxel monotherapy every three weeks were included. To assess quality of toxicity reporting, the Consolidated Standards of Reporting Trials (CONSORT) harms checklist was adapted and each trial scored by two independent reviewers. CONSORT scores as well as PSA and radiological response rates over time were examined with Spearman correlation coefficients. Univariable and multivariable linear regression examined associations between scores and phase II versus III trials, publication year, midpoint of accrual, number of patients, sponsor type, journal impact factor, presence of supplementary data, and geographical region. Results: From 21 clinical trials including 5,460 patients in docetaxel monotherapy arms, the median CONSORT score was 15.3 (IQR 13.7–16.5) out of 22. Correlation coefficients were not significant for all comparisons of CONSORT scores and response rates versus years of accrual or year of publication. In univariable linear regression, phase III clinical trials were associated with a significantly higher CONSORT score (p = 0.01) as was a journal impact factor greater than 15 (p = 0.02). In exploratory analyses, none of the examined factors were significant in multivariable linear regression. Conclusions: CONSORT scores and thus toxicity reporting quality in CRPC trials studying docetaxel show need for improvement and should be subject to further discussion. There has been no significant improvement in toxicity reporting quality over time. It remains to be studied if our findings also apply to other agents used for the treatment of CRPC. Legal entity responsible for the study: Sunnybrook Research Institute. Funding: Joseph and Silvana Melara Cancer Fund. Disclosure: All authors have declared no conflicts of interest.

Hepatic effects assessed by review of safety data in enzalutamide castration-resistant prostate cancer (CRPC) trials.

199 Background: Androgen receptor inhibitor enzalutamide (ENZA) improves survival in patients with metastatic CRPC. As the liver is the main route of ENZA elimination, this post hoc analysis evaluated the hepatic effects of ENZA versus comparators in controlled CRPC trials. Methods: Safety data from two large Phase 3, placebo (PBO)- (PREVAIL, NCT0121299; AFFIRM, NCT00974311) and two smaller Phase 2, bicalutamide (BIC)-controlled (STRIVE, NCT01664923; TERRAIN, NCT01288911) ENZA trials in men with CRPC were assessed for hepatic impairment-related adverse events (AEs) using the following standardized narrow MedDRA queries V19.1: hepatic failure, fibrosis and cirrhosis, and other liver damage-related conditions; hepatitis, non-infectious; and liver-related investigation, signs, and symptoms. Liver-related laboratory test results were also evaluated. Data were summarized as follows: patients receiving ENZA in Phase 3 trials (n = 1671); patients receiving ENZA in Phase 2 trials (n = 380); patients receiving PBO (n = 1243); patients receiving BIC (n = 387); and combined ENZA-treated patients (n = 2051). Results: Percentages of hepatic impairment-related AEs ranged between 2.9% and 4.5% with ENZA, and were 2.7% with PBO and 5.4% with BIC (Table). The most common hepatic impairment-related AEs were increased aspartate (AST) and alanine aminotransferase (ALT; Table). Within each trial, the incidences of grade ≥3 AEs were similar, and dose reductions or discontinuations due to hepatic impairment-related AEs were low (Table). When adjusted for treatment exposure, AEs per 100 patient-years were lower with ENZA versus either PBO or BIC (Table). Conclusions: This combined analysis of CRPC trials demonstrates no hepatic safety signal with ENZA and thus routine liver tests are not required. Clinical trial information: NCT0121299; NCT00974311; NCT01664923; NCT01288911. [Table: see text]

Resistance to BET Inhibitor Leads to Alternative Therapeutic Vulnerabilities in Castration-Resistant Prostate Cancer

BRD4 plays a major role in the transcription networks orchestrated by androgen receptor (AR) in castration-resistant prostate cancer (CRPC). Several BET inhibitors (BETi) that displace BRD4 from chromatin are being evaluated in clinical trials for CRPC. Here, we describe mechanisms of acquired resistance to BETi that are amenable to targeted therapies in CRPC. BETi-resistant CRPC cells displayed cross-resistance to a variety of BETi in the absence of gatekeeper mutations, exhibited reduced chromatin-bound BRD4, and were less sensitive to BRD4 degraders/knockdown, suggesting a BRD4-independent transcription program. Transcriptomic analysis revealed reactivation of AR signaling due to CDK9-mediated phosphorylation of AR, resulting in sensitivity to CDK9 inhibitors and enzalutamide. Additionally, increased DNA damage associated with PRC2-mediated transcriptional silencing of DDR genes was observed, leading to PARP inhibitor sensitivity. Collectively, our results identify the therapeutic limitation of BETi as a monotherapy; however, our BETi resistance data suggest unique opportunities for combination therapies in treating CRPC.

Bone turnover biomarkers identify unique prognostic risk groups in men with castration resistant prostate cancer and skeletal metastases: Results from SWOG S0421

BackgroundSkeletal metastases often occur in men with castration-resistant prostate cancer (CRPC) where bone biomarkers are prognostic for overall survival (OS). In those with highly elevated markers, there is preferential benefit from bone-targeted therapy. In the phase IIIS0421 docetaxel +/− atrasentan trial, clinical covariates and bone biomarkers were analyzed to identify CRPC subsets with differential outcomes. Subjects and methodsMarkers of bone resorption [N-telopeptide-NTx; pyridinoline-PYD] and formation [C-terminal collagen propeptide-CICP; bone alkaline phosphatase-BAP] were measured in pre-treatment sera. Bone biomarkers and clinical covariates were included in a Cox model for OS; bone markers were added in a stepwise selection process. Receiver operating characteristic (ROC) curves were constructed for risk factor models +/− bone markers. Significant variables were allowed to compete in a classification and regression tree (CART) analysis. Hazard ratios(HR) were calculated by comparing OS in each of the terminal nodes to a reference group in a Cox model. Results750 patients were included. Each bone marker significantly contributed to the risk factor-adjusted OS Cox model, with higher levels associated with worse OS. BAP (HR = 1.15, p = 0.008), CICP (HR = 1.27, p < 0.001), and PYD (HR = 1.21, p = 0.047) in combination were significantly associated with OS. Prognostic accuracy was improved by addition of bone markers to clinical covariates. CART analysis selected CICP, BAP, hemoglobin, and pain score for the final OS model, identifying five prognostic groups. ConclusionsElevated serum bone biomarker levels are associated with worse OS in bone-metastatic CRPC. Bone biomarkers can identify unique prognostic subgroups. These results further define the role of bone biomarkers in the design of CRPC trials.

Abstract 1459: Dual-strand tumor-suppressor microRNA-145 (miR-145-5p and miR-145-3p) are involved in castration-resistant prostate cancer pathogenesis

Abstract Prostate cancer (PCa) is the most frequently diagnosed cancer and the second leading cause of cancer-related death among men in developed countries. Androgen signaling through the androgen receptor (AR) is an important oncogenic pathway for PCa progression. Most patients initially respond to androgen-deprivation therapy (ADT), but eventually acquire resistance and progress to castration-resistant prostate cancer (CRPC). Although several clinical trials for CRPC have been carried out, resulting in the availability of novel chemotherapeutic agents, these treatments provide limited benefits and are not considered curative. Therefore, identification of effective biomarkers for detection of CRPC and understanding the molecular mechanisms of androgen-independent signaling and metastatic signaling pathways underlying PCa using current genomic approaches would help to improve therapies for and prevention of the disease. The discovery of microRNAs (miRNAs) has resulted in major advancements in cancer research. miRNAs are small noncoding RNAs that function to fine tune the expression of protein coding/noncoding RNAs by repressing translation or cleaving RNA transcripts in a sequence-depending manner. The unique characteristic function of miRNAs is to regulate RNA transcripts in human cells. Therefore, dysregulated expression of miRNAs can disrupt tightly regulated RNA networks in cancer cells. miRNAs play critical roles in various biological processes, and their dysregulation is shown in several human cancers. In this study, we constructed the miRNA expression signature of CRPC using clinical specimens because the development of therapeutic strategies is a central theme in the advancement of PCa treatments. Using CRPC expression signature data, we investigated the specific roles of miRNAs in PCa and CRPC oncogenesis by examining differentially expressed miRNAs. Based on the CRPC signature, we focused on the dual strand of pre-miR-145, miR-145-5p and miR-145-3p because these miRNAs were significantly reduced in cancer tissues, suggesting these miRNAs act as antitumor miRNAs in this disease. In miRNA biogenesis, it is the general consensus that processing of the pre-miRNA through Dicer1 generates a miRNA duplex (a passenger strand and a guide strand), and that the passenger strand has degradation and no regulatory activity and disintegrates in cells. Our present data showed that both miRNAs, miR-145-5p and miR-145-3p significantly suppressed cancer cell migration and invasion. Moreover, Kaplan-Meier survival curves showed that low expression of miR-145-3p predicted a short duration of progression to CRPC. Dual strand of pre-miR-145 functioned as tumor suppressors based on the miRNA expression signature of CRPC. Identification of miRNA-mediated cancer networks may provide novel molecular pathogenesis of the disease. Citation Format: Mayuko Kato, Akira Kurozumi, Yusuke Goto, Nijiro Nohata, Takayuki Arai, Atsushi Okato, Keiichi Koshizuka, Satoko Kojima, Tomohiko Ichikawa, Naohiko Seki. Dual-strand tumor-suppressor microRNA-145 (miR-145-5p and miR-145-3p) are involved in castration-resistant prostate cancer pathogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1459. doi:10.1158/1538-7445.AM2017-1459

Abstract 5220: Chronic exposure to a novel AR-NTD inhibitor induces resistance via a selective metabolism pathway

Abstract Background: The androgen receptor (AR) is recognized as playing a crucial role in prostate cancer (PCa) maintenance and progression; therefore its inhibition has been the cornerstone of modern therapy for men who fail primary treatment. Current treatments are initially effective, however resistance ultimately develops and the disease progresses to a lethal form termed castration-resistant prostate cancer (CRPC). Our lab has discovered a new class of molecules (EPI) which inhibit the AR by binding to the N-terminal domain (NTD). The NTD interacts with transcriptional machinery, and its presence is vital for a transcriptionally functional receptor. We have previously shown that EPI-002 specifically inhibits both full-length AR and constitutively active AR splice variants. The efficacy of EPI-506, the prodrug of EPI-002, is currently being tested in a Phase I/II clinical trial for CRPC. Here we propose novel resistance mechanisms arising from sustained AR-NTD inhibition, with the goal of preemptively developing backup compounds. Methods: The androgen sensitive human PCa cell line LNCaP was used in all experiments. A resistant cell line (LNCaP-EPIR) was generated by passaging parental LNCaP cells weekly in media supplemented with EPI-002 beginning in September 2012. In vitro and in vivo studies using LNCaP and LNCaP-EPIR cells were employed to confirm biological resistance. A human affymetrix microarray identified possible resistance mechanisms and was validated using qRT-PCR, western blot and functional studies. LNCaP and LNCaP-EPIR cells were challenged with EPI-045, an EPI-analog predicted to remain effective in the context of EPI-002 resistance. Results: LNCaP-EPIR cells treated with 25 µM EPI-002 displayed similar growth rates to vehicle treatment, both in vitro and in vivo. Conversely, parental LNCaP cells showed significant growth inhibition in response to EPI-002. LNCaP-EPIR cells retained sensitivity to anti-androgens and AR knock-down by targeted siRNA, implying functional AR remains essential for growth. qRT-PCR data demonstrated that EPI-002 had reduced ability to block AR mediated gene transcription. Interrogation of microarray data revealed candidate genes (UGT2B family) which were specifically upregulated in the resistant line, and may function to metabolize EPI-002. Supporting this hypothesis EPI-045 which is predicted to be resistant to UGT2B metabolism, was able to significantly inhibit LNCaP-EPIR proliferation and AR transcriptional activity. Conclusions: Taken together these data suggest an EPI-specific mechanism of resistance, whereby EPI-002 is preferentially metabolized and removed from the cell. LNCaP-EPIR cells remain dependent upon AR signalling, and are sensitive to anti-androgens used clinically as well as a novel EPI-analog. This work highlights the potential for combination or sequential therapy in the context of drug-resistant CRPC. Citation Format: Jonathon K. Obst, Jun Wang, David Williams, Amy H. Tien, Nasrin R. Mawji, Yu Chi Yang, Raymond J. Andersen, Marianne D. Sadar. Chronic exposure to a novel AR-NTD inhibitor induces resistance via a selective metabolism pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5220. doi:10.1158/1538-7445.AM2017-5220

Steroidogenic Metabolism of Galeterone Reveals a Diversity of Biochemical Activities

Galeterone is a steroidal CYP17A1 inhibitor, androgen receptor (AR) antagonist, and AR degrader, under evaluation in a phase III clinical trial for castration-resistant prostate cancer (CRPC). The A/B steroid ring (Δ5,3β-hydroxyl) structure of galeterone is identical to that of cholesterol, which makes endogenous steroids with the same structure (e.g., dehydroepiandrosterone and pregnenolone) substrates forthe enzyme 3β-hydroxysteroid dehydrogenase (3βHSD). We found that galeterone is metabolized by 3βHSD to Δ4-galeterone (D4G), which is further converted by steroid-5α-reductase (SRD5A) to 3-keto-5α-galeterone (5αG), 3α-OH-5α-galeterone, and 3β-OH-5α-galeterone; invivo it is also converted to the three corresponding 5β-reduced metabolites. D4G inhibits steroidogenesis and suppresses AR protein stability, AR target gene expression, and xenograft growth comparably with galeterone, and further conversion by SRD5A leads to loss of several activities that inhibit the androgen axis that may compromise clinical efficacy. Together, these findings define a critical metabolic class effect of steroidal drugs with a Δ5,3β-hydroxyl structure.

Abstract 1100: Targeting ITGA3/ITGB1 signaling by tumor-suppressive microRNA-223 inhibits cancer cell migration and invasion in prostate cancer

Abstract BACKGROUNDS: Most patients initially respond to androgen-deprivation therapy, but eventually acquire resistance and progress to castration-resistant prostate cancer (CRPC). Several clinical trials for CRPC have shown limited benefits, eventually resulting in disease progression and metastasis. Our recent study of microRNA (miRNA) expression signature in CRPC revealed that miR-223 expression was significantly reduced in PCa tissues, suggesting miR-223 functions as a tumor suppressive miRNA in PCa cells. The aim of this study was to investigate the functional significance of miR-223 and to identify its regulated oncogenic genes in PCa. METHODS: Expression levels of miR-223 were evaluated in PCa clinical specimens and PCa cell lines (PC3 and PC3M) by quantitative real-time PCR methods. Gain-of-function studies (cell proliferation, migration and invasion assays) were performed using transfection of mature miR-223 into cancer cells. Genome-wide gene expression analysis and in silico analysis were applied to investigate molecular targets regulated by miR-223 in PCa cells. A luciferase reporter assay was carried out to determine whether 3’ UTR of target genes have actual biding sites for miR-223. To investigate the functional role of target genes in PCa cells, loss-of-function studies by silencing of these genes were performed. RESULTS: The expression levels of miR-223 were significantly reduced in PCa clinical specimens and cell lines compared to non-cancerous prostate tissues. Restoration of miR-223 significantly inhibits cancer cell migration and invasion in PCa cells. Integrin alpha-3 (ITGA3) and integrin beta-1 (ITGB1) were identified as direct target genes of miR-223 by microarray, in silico studies, and luciferase reporter assays. ITGA3 and ITGB1 interact with multiple extracellular matrix proteins and mediate several survival signaling into the cancer cells. Knockdown of ITGA3 and ITGB1 significantly inhibited cancer cell migration and invasion in PCa cells by regulating downstream signaling. CONCLUSIONS: Downregulation of miR-223 was a frequent event of PCa cells and it functions as a tumor suppressor via targeting ITGA3 and ITGB1. Overexpression of ITGA3 or ITGB1 might be contributed to PCa oncogenesis and metastasis. Elucidation of tumor-suppressive miR-223 regulated molecular pathways and targets could provide new information on potential therapeutic strategies in PCa. Citation Format: Ichiro Fukumoto, Akira Kurozumi, Yusuke Goto, Ryosuke Matsushita, Mayuko Kato, Rika Nishikawa, Shinichi Sakamoto, Tomohiko Ichikawa, Naohiko Seki. Targeting ITGA3/ITGB1 signaling by tumor-suppressive microRNA-223 inhibits cancer cell migration and invasion in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1100.

Abstract 608: Comprehensive drug testing of patient-derived conditionally reprogrammed cells from castration-resistant prostate cancer

Abstract Culture of human prostate cancer (PCa) progenitor cells would facilitate the discovery and testing of new, potentially curative therapies for PCa. Here, we established and characterized patient-derived conditionally reprogrammed cells (CRCs) from seven patients to determine their biological properties (genomic, transcriptomic, protein expression) and to apply these cells to test efficacies of 306 emerging and clinically approved drugs. The patient samples came from both primary prostate cancer as well as from advanced Castration-Resistant Prostate Cancer (CRPC). Patients with primary prostate cancer generated six benign CRC cultures which all had an androgen receptor (AR)-negative, basal/transit-amplifying phenotype with few CNAs. In 3D cell culture, these cells could re-express AR. The CRCs from a CRPC patient (HUB.5) displayed multiple CNAs, many of which were shared with the parental tumor. We carried out high-throughput drug-response studies with 306 emerging and clinical cancer drugs. Bcl-2 family inhibitor navitoclax emerged as the most potent cancer-specific drug for the CRCs from CRPC patient. Other drug efficacies observed included taxanes, mepacrine and retinoids, thus covering both existing (and clinically validated) as well as new drug efficacies. In conclusion, comprehensive cancer-pharmacopeia-wide drug testing of CRCs from a CRPC patient highlighted both known and novel drug sensitivities in PCa, including navitoclax, which is currently tested in clinical trials of CRPC. Citation Format: Khalid Saeed, Vesa Rahkama, Samuli Eldfors, Dmitrii Bychkov, John Patrick Mpindi, Bhagwan Yadav, Tero Aittokallio, Peter Horvath, Donna Peehl, Lassi Paavolainen, Caroline Heckman, Krister Wennerberg, Tuomas Mirtti, Antti Rannikko, Olli Kallioniemia, Päivi Östling, Taija af Hällström. Comprehensive drug testing of patient-derived conditionally reprogrammed cells from castration-resistant prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 608.

Comprehensive Drug Testing of Patient-derived Conditionally Reprogrammed Cells from Castration-resistant Prostate Cancer

BackgroundTechnology development to enable the culture of human prostate cancer (PCa) progenitor cells is required for the identification of new, potentially curative therapies for PCa. ObjectiveWe established and characterized patient-derived conditionally reprogrammed cells (CRCs) to assess their biological properties and to apply these to test the efficacies of drugs. Design, setting, and participantsCRCs were established from seven patient samples with disease ranging from primary PCa to advanced castration-resistant PCa (CRPC). The CRCs were characterized by genomic, transcriptomic, protein expression, and drug profiling. Outcome measurements and statistical analysisThe phenotypic quantification of the CRCs was done based on immunostaining followed by image analysis with Advanced Cell Classifier using Random Forest supervised machine learning. Copy number aberrations (CNAs) were called from whole-exome sequencing and transcriptomics using in-house pipelines. Dose-response measurements were used to generate multiparameter drug sensitivity scores using R-statistical language. Results and limitationsWe generated six benign CRC cultures which all had an androgen receptor-negative, basal/transit-amplifying phenotype with few CNAs. In three-dimensional cell culture, these cells could re-express the androgen receptor. The CRCs from a CRPC patient (HUB.5) displayed multiple CNAs, many of which were shared with the parental tumor. We carried out high-throughput drug-response studies with 306 emerging and clinical cancer drugs. Using the benign CRCs as controls, we identified the Bcl-2 family inhibitor navitoclax as the most potent cancer-specific drug for the CRCs from a CRPC patient. Other drug efficacies included taxanes, mepacrine, and retinoids. ConclusionsComprehensive cancer pharmacopeia-wide drug testing of CRCs from a CRPC patient highlighted both known and novel drug sensitivities in PCa, including navitoclax, which is currently being tested in clinical trials of CRPC. Patient summaryWe describe an approach to generate patient-derived cancer cells from advanced prostate cancer and apply such cells to discover drugs that could be applied in clinical trials for castration-resistant prostate cancer.

Discovery of ODM-201, a new-generation androgen receptor inhibitor targeting resistance mechanisms to androgen signaling-directed prostate cancer therapies.

Activation of androgen receptor (AR) is crucial for prostate cancer growth. Remarkably, also castration-resistant prostate cancer (CRPC) is dependent on functional AR, and several mechanisms have been proposed to explain the addiction. Known causes of CRPC include gene amplification and overexpression as well as point mutations of AR. We report here the pharmacological profile of ODM-201, a novel AR inhibitor that showed significant antitumor activity and a favorable safety profile in phase 1/2 studies in men with CRPC. ODM-201 is a full and high-affinity AR antagonist that, similar to second-generation antiandrogens enzalutamide and ARN-509, inhibits testosterone-induced nuclear translocation of AR. Importantly, ODM-201 also blocks the activity of the tested mutant ARs arising in response to antiandrogen therapies, including the F876L mutation that confers resistance to enzalutamide and ARN-509. In addition, ODM-201 reduces the growth of AR-overexpressing VCaP prostate cancer cells both in vitro and in a castration-resistant VCaP xenograft model. In contrast to other antiandrogens, ODM-201 shows negligible brain penetrance and does not increase serum testosterone levels in mice. In conclusion, ODM-201 is a potent AR inhibitor that overcomes resistance to AR-targeted therapies by antagonizing both overexpressed and mutated ARs. ODM-201 is currently in a phase 3 trial in CRPC.

The Prostate Cancer Working Group 3 (PCWG3) consensus for trials in castration-resistant prostate cancer (CRPC).

5000 Background: The availability of new agents for men with CRPC, recognition of new disease phenotypes, and an evolving regulatory environment have created the need for new CRPC clinical trial gu...

MP73-12 UNSUSPECTED METASTASES FOUND DURING SCREENING FOR A TRIAL OF PATIENTS WITH NON-METASTATIC CASTRATION RESISTANT PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Advanced I1 Apr 2015MP73-12 UNSUSPECTED METASTASES FOUND DURING SCREENING FOR A TRIAL OF PATIENTS WITH NON-METASTATIC CASTRATION RESISTANT PROSTATE CANCER E. David Crawford, Jannell R. DePalantino, Philip W. Kantoff, Neal Shore, Willie Underwood, Vijay Reddy, Jim Wang, Suneel Mundle, Zane Yang, Tracy McGowan, and Charles J. Ryan E. David CrawfordE. David Crawford More articles by this author , Jannell R. DePalantinoJannell R. DePalantino More articles by this author , Philip W. KantoffPhilip W. Kantoff More articles by this author , Neal ShoreNeal Shore More articles by this author , Willie UnderwoodWillie Underwood More articles by this author , Vijay ReddyVijay Reddy More articles by this author , Jim WangJim Wang More articles by this author , Suneel MundleSuneel Mundle More articles by this author , Zane YangZane Yang More articles by this author , Tracy McGowanTracy McGowan More articles by this author , and Charles J. RyanCharles J. Ryan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.2688AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Factors associated with rates of progression from non-metastatic to metastatic castration resistant prostate cancer (CRPC) have been described.1,2 We used this information to identify patients at high risk for progression from non-metastatic to metastatic disease (MD) for entry into the IMpact of Abiraterone Acetate in Prostate Specific AntiGEN (IMAAGEN) trial. To report the high rate of unsuspected metastases in asymptomatic patients with CRPC, leading to screen failure. METHODS From April 2011-July 2013, patients were screened for entry into the IMAAGEN trial. Key entry criteria included having CRPC as defined by a rising PSA and a serum T < 50 ng/dL and a PSA ≥ 10 ng/mL or PSA doubling time (PSADT) ≤ 10 months. Primary endpoint of IMAAGEN was proportion of subjects achieving a ≥ 50% reduction in PSA by 6 cycles of treatment. During screening, patients who met entry criteria based on laboratory results underwent imaging studies to screen for local disease progression or MD. RESULTS 298 patients were screened. 167 (56%) patients screen failed. 77 patients had MD, which represents 37% of 208 patients who, by lab results, were eligible for and underwent imaging studies. We will report on the relationship of unsuspected MD to PSA/PSADT entry criteria. CONCLUSIONS A high rate of unsuspected asymptomatic MD was found in this high-risk CRPC patient population (PSA ≥ 10 ng/mL or PSADT ≤ 10months). Our findings build upon other reported data on MD discovered during screening for non-metastatic CRPC trials.3 These findings suggest the need to prospectively define risk factors for development of MD in CRPC to assure timely identification, especially in light of new treatment options. 1Smith MR, Kabbinavar F, Saad F et al. Natural History of Rising Serum Prostate-Specific Antigen in Men with Castrate Nonmetastatic Prostate Cancer. J Clin Oncol 2005;23:2918-2925. 2Smith MR, Cook R, Lee K et al. Disease and Host Characteristics as Predictors of Time to First Bone Metastasis and Death in Men with Progressive Castration-Resistant Nonmetastatic Prostate Cancer. Cancer 2011;117:2077-85. 3Yu EY, Miller K, Nelson J et al. Detection of previously unidentified metastatic disease as a leading cause of screening failure in a phase III trial of zibotentan versus placebo in patients with nonmetastatic, castration resistant prostate cancer. J Urol 2012;188:103-109. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e934 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information E. David Crawford More articles by this author Jannell R. DePalantino More articles by this author Philip W. Kantoff More articles by this author Neal Shore More articles by this author Willie Underwood More articles by this author Vijay Reddy More articles by this author Jim Wang More articles by this author Suneel Mundle More articles by this author Zane Yang More articles by this author Tracy McGowan More articles by this author Charles J. Ryan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...