Abstract
The androgen receptor (AR) is the critical driver in prostate cancer and exerts its function mainly through transcriptional control. Recent advances in clinical studies and cell line models ...have illustrated that AR chromatin binding features are not static; rather they are highly variable yet reproducibly altered between clinical stages. Extensive genomic analyses of AR chromatin binding features in different disease stages have revealed a high degree of plasticity of AR chromatin interactions in clinical samples. Mechanistically, AR chromatin binding patterns are associated with specific somatic mutations on AR and other permutations, including mutations of AR-interacting proteins. Here we summarize the most recent studies on how the AR cistrome is dynamically altered in prostate cancer models and patient samples, and what implications this has for the identification of therapeutic targets to avoid the emergence of treatment resistance.
Summary Background Ipilimumab is a fully human monoclonal antibody that binds cytotoxic T-lymphocyte antigen 4 to enhance antitumour immunity. Our aim was to assess the use of ipilimumab after ...radiotherapy in patients with metastatic castration-resistant prostate cancer that progressed after docetaxel chemotherapy. Methods We did a multicentre, randomised, double-blind, phase 3 trial in which men with at least one bone metastasis from castration-resistant prostate cancer that had progressed after docetaxel treatment were randomly assigned in a 1:1 ratio to receive bone-directed radiotherapy (8 Gy in one fraction) followed by either ipilimumab 10 mg/kg or placebo every 3 weeks for up to four doses. Non-progressing patients could continue to receive ipilimumab at 10 mg/kg or placebo as maintenance therapy every 3 months until disease progression, unacceptable toxic effect, or death. Patients were randomly assigned to either treatment group via a minimisation algorithm, and stratified by Eastern Cooperative Oncology Group performance status, alkaline phosphatase concentration, haemoglobin concentration, and investigator site. Patients and investigators were masked to treatment allocation. The primary endpoint was overall survival, assessed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov , number NCT00861614. Findings From May 26, 2009, to Feb 15, 2012, 799 patients were randomly assigned (399 to ipilimumab and 400 to placebo), all of whom were included in the intention-to-treat analysis. Median overall survival was 11·2 months (95% CI 9·5–12·7) with ipilimumab and 10·0 months (8·3–11·0) with placebo (hazard ratio HR 0·85, 0·72–1·00; p=0·053). However, the assessment of the proportional hazards assumption showed that it was violated (p=0·0031). A piecewise hazard model showed that the HR changed over time: the HR for 0–5 months was 1·46 (95% CI 1·10–1·95), for 5–12 months was 0·65 (0·50–0·85), and beyond 12 months was 0·60 (0·43–0·86). The most common grade 3–4 adverse events were immune-related, occurring in 101 (26%) patients in the ipilimumab group and 11 (3%) of patients in the placebo group. The most frequent grade 3–4 adverse events included diarrhoea (64 16% of 393 patients in the ipilimumab group vs seven 2% of 396 in the placebo group), fatigue (40 11% vs 35 9%), anaemia (40 10% vs 43 11%), and colitis (18 5% vs 0). Four (1%) deaths occurred because of toxic effects of the study drug, all in the ipilimumab group. Interpretation Although there was no significant difference between the ipilimumab group and the placebo group in terms of overall survival in the primary analysis, there were signs of activity with the drug that warrant further investigation. Funding Bristol-Myers Squibb.
Epigenetic processes govern prostate cancer (PCa) biology, as evidenced by the dependency of PCa cells on the androgen receptor (AR), a prostate master transcription factor. We generated 268 ...epigenomic datasets spanning two state transitions-from normal prostate epithelium to localized PCa to metastases-in specimens derived from human tissue. We discovered that reprogrammed AR sites in metastatic PCa are not created de novo; rather, they are prepopulated by the transcription factors FOXA1 and HOXB13 in normal prostate epithelium. Reprogrammed regulatory elements commissioned in metastatic disease hijack latent developmental programs, accessing sites that are implicated in prostate organogenesis. Analysis of reactivated regulatory elements enabled the identification and functional validation of previously unknown metastasis-specific enhancers at HOXB13, FOXA1 and NKX3-1. Finally, we observed that prostate lineage-specific regulatory elements were strongly associated with PCa risk heritability and somatic mutation density. Examining prostate biology through an epigenomic lens is fundamental for understanding the mechanisms underlying tumor progression.
Metastatic castration-resistant prostate cancer (mCRPC) has a highly complex genomic landscape. With the recent development of novel treatments, accurate stratification strategies are needed. Here we ...present the whole-genome sequencing (WGS) analysis of fresh-frozen metastatic biopsies from 197 mCRPC patients. Using unsupervised clustering based on genomic features, we define eight distinct genomic clusters. We observe potentially clinically relevant genotypes, including microsatellite instability (MSI), homologous recombination deficiency (HRD) enriched with genomic deletions and BRCA2 aberrations, a tandem duplication genotype associated with CDK12
and a chromothripsis-enriched subgroup. Our data suggests that stratification on WGS characteristics may improve identification of MSI, CDK12
and HRD patients. From WGS and ChIP-seq data, we show the potential relevance of recurrent alterations in non-coding regions identified with WGS and highlight the central role of AR signaling in tumor progression. These data underline the potential value of using WGS to accurately stratify mCRPC patients into clinically actionable subgroups.
Abstract
The androgen receptor (AR) is the master regulator of prostate cancer (PCa) development, and inhibition of AR signalling is the most effective PCa treatment. AR is expressed in PCa cells and ...also in the PCa-associated stroma, including infiltrating macrophages. Macrophages have a decisive function in PCa initiation and progression, but the role of AR in macrophages remains largely unexplored. Here, we show that AR signalling in the macrophage-like THP-1 cell line supports PCa cell line migration and invasion in culture via increased Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) signalling and expression of its downstream cytokines. Moreover, AR signalling in THP-1 and monocyte-derived macrophages upregulates IL-10 and markers of tissue residency. In conclusion, our data suggest that AR signalling in macrophages may support PCa invasiveness, and blocking this process may constitute one mechanism of anti-androgen therapy.
Deletion of the gene encoding the chromatin remodeler CHD1 is among the most common alterations in prostate cancer (PCa); however, the tumor-suppressive functions of CHD1 and reasons for its ...tissue-specific loss remain undefined. We demonstrated that CHD1 occupied prostate-specific enhancers enriched for the androgen receptor (AR) and lineage-specific cofactors. Upon CHD1 loss, the AR cistrome was redistributed in patterns consistent with the oncogenic AR cistrome in PCa samples and drove tumor formation in the murine prostate. Notably, this cistrome shift was associated with a unique AR transcriptional signature enriched for pro-oncogenic pathways unique to this tumor subclass. Collectively, these data credential CHD1 as a tumor suppressor in the prostate that constrains AR binding/function to limit tumor progression.
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•CHD1 acts as a prostate-specific tumor suppressor in vivo•CHD1 regulates AR occupancy at a subset of lineage-specific enhancers•Loss of CHD1 redistributes the AR cistrome to favor oncogenic AR-driven pathways
Augello et al. show that CHD1 binds prostate-specific enhancers enriched for the androgen receptor (AR). Upon CHD1 loss, which occurs often in prostate cancer (PCa), the AR cistrome changes to be consistent with that in PCa and is associated with an AR transcriptional signature unique to this subclass of PCa.
Thousands of noncoding somatic single-nucleotide variants (SNVs) of unknown function are reported in tumors. Partitioning the genome according to cistromes reveals the enrichment of somatic SNVs in ...prostate tumors as opposed to adjacent normal tissue cistromes of master transcription regulators, including AR, FOXA1, and HOXB13. This parallels enrichment of prostate cancer genetic predispositions over these transcription regulators' tumor cistromes, exemplified at the 8q24 locus harboring both risk variants and somatic SNVs in cis-regulatory elements upregulating MYC expression. However, Massively Parallel Reporter Assays reveal that few SNVs can alter the transactivation potential of individual cis-regulatory elements. Instead, similar to inherited risk variants, SNVs accumulate in cistromes of master transcription regulators required for prostate cancer development.
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•Cistrome partitioning reveals convergence of somatic and risk-variant SNVs•Somatic SNVs enrich within the tumor-defined as opposed to normal-defined cistromes•Somatic SNVs can modulate the output from CREs, such as seen at the MYC locus•Few SNVs alter CREs but collectively target essential transcription regulators
Mazrooei et al. show that somatic SNVs are enriched in cistromes of master transcription regulators in prostate cancers but not in adjacent normal tissues. Few SNVs alter CREs but collectively target essential transcription regulators.
Summary Background Clusterin is a chaperone protein associated with treatment resistance and upregulated by apoptotic stressors such as chemotherapy. Custirsen is a second-generation antisense ...oligonucleotide that inhibits clusterin production. The aim of the SYNERGY trial was to investigate the effect of custirsen in combination with docetaxel and prednisone on overall survival in patients with metastatic castration-resistant prostate cancer. Methods SYNERGY was a phase 3, multicentre, open-label, randomised trial set at 134 study centres in 12 countries. Patients were eligible for participation if they had: metastatic castration-resistant prostate cancer and had received no previous chemotherapy; prostate-specific antigen greater than 5 ng/mL; and a Karnofsky performance score of 70% or higher. Patients were randomly assigned 1:1 centrally to either the docetaxel, prednisone, and custirsen combination or docetaxel and prednisone alone. Patients were not masked to treatment allocation. Randomisation was stratified by opioid use for cancer-related pain and radiographic evidence of progression. All patients received docetaxel 75 mg/m2 intravenously with 5 mg of prednisone orally twice daily. Patients assigned docetaxel, prednisone, and custirsen received weekly doses of custirsen 640 mg intravenously after three loading doses of 640 mg. The primary endpoint was overall survival analysed in the intention-to-treat population. Patients who received at least one study dose were included in the safety analysis set. This trial is registered with ClinicalTrials.gov , number NCT01188187 . The trial is completed and final analyses are reported here. Findings Between Dec 10, 2010, and Nov 7, 2012, 1022 patients were enrolled to the trial, of whom 510 were assigned docetaxel, prednisone, and custirsen and 512 were allocated docetaxel and prednisone. No difference in overall survival was recorded between the two groups (median survival 23·4 months 95% CI 20·9–24·8 with docetaxel, prednisone, and custirsen vs 22·0 months 19·5–24·0 with docetaxel and prednisone; hazard ratio HR 0·93, 95% CI 0·79–1·10; p=0·415). The most common adverse events of grade 3 or worse in the docetaxel, prednisone and custirsen group (n=501) compared with the docetaxel and prednisone alone group (n=499) were neutropenia (grade 3, 63 13% vs 28 6%; grade 4, 98 20% vs 77 15%), febrile neutropenia (grade 3, 52 10% vs 31 6%; grade 4, four 1% vs two <1%), and fatigue (grade 3, 53 11% vs 41 8%; grade 4, three 1% vs one <1%). One or more serious adverse events were reported for 214 (43%) of 501 patients treated with docetaxel, prednisone, and custirsen and 181 (36%) of 499 receiving docetaxel and prednisone alone. Adverse events were attributable to 23 (5%) deaths in the docetaxel, prednisone, and custirsen group and 24 (5%) deaths in the docetaxel and prednisone alone group. Interpretation Addition of custirsen to first-line docetaxel and prednisone was reasonably well tolerated, but overall survival was not significantly longer for patients with metastatic castration-resistant prostate cancer treated with this combination, compared with patients treated with docetaxel and prednisone alone. Funding OncoGenex Technologies.
The androgen receptor drives the growth of metastatic castration-resistant prostate cancer. This has led to the development of multiple novel drugs targeting this hormone-regulated transcription ...factor, such as enzalutamide – a potent androgen receptor antagonist. Despite the plethora of possible treatment options, the absolute survival benefit of each treatment separately is limited to a few months. Therefore, current research efforts are directed to determine the optimal sequence of therapies, discover novel drugs effective in metastatic castration-resistant prostate cancer and define patient subpopulations that ultimately benefit from these treatments. Molecular studies provide evidence on which pathways mediate treatment resistance and may lead to improved treatment for metastatic castration-resistant prostate cancer. This review provides, firstly a concise overview of the clinical development, use and effectiveness of enzalutamide in the treatment of advanced prostate cancer, secondly it describes translational research addressing enzalutamide response vs resistance and lastly highlights novel potential treatment strategies in the enzalutamide-resistant setting.
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