Inhibition of EZH2 transactivation function sensitizes solid tumors to genotoxic stress

Drugs that block the activity of the methyltransferase EZH2 are in clinical development for the treatment of non-Hodgkin lymphomas harboring EZH2 gain-of-function mutations that enhance its polycomb repressive function. We have previously reported that EZH2 can act as a transcriptional activator in castration-resistant prostate cancer (CRPC). Now we show that EZH2 inhibitors can also block the transactivation activity of EZH2 and inhibit the growth of CRPC cells. Gene expression and epigenomics profiling of cells treated with EZH2 inhibitors demonstrated that in addition to derepressing gene expression, these compounds also robustly down-regulate a set of DNA damage repair (DDR) genes, especially those involved in the base excision repair (BER) pathway. Methylation of the pioneer factor FOXA1 by EZH2 contributes to the activation of these genes, and interaction with the transcriptional coactivator P300 via the transactivation domain on EZH2 directly turns on the transcription. In addition, CRISPR-Cas9–mediated knockout screens in the presence of EZH2 inhibitors identified these BER genes as the determinants that underlie the growth-inhibitory effect of EZH2 inhibitors. Interrogation of public data from diverse types of solid tumors expressing wild-type EZH2 demonstrated that expression of DDR genes is significantly correlated with EZH2 dependency and cellular sensitivity to EZH2 inhibitors. Consistent with these findings, treatment of CRPC cells with EZH2 inhibitors dramatically enhances their sensitivity to genotoxic stress. These studies reveal a previously unappreciated mechanism of action of EZH2 inhibitors and provide a mechanistic basis for potential combination cancer therapies.

Expression of Fibroblast Activation Protein Is Enriched in Neuroendocrine Prostate Cancer and Predicts Worse Survival

Background: Advanced prostate cancer (PC) may accumulate genomic alterations that hallmark lineage plasticity and transdifferentiation to a neuroendocrine (NE) phenotype. Fibroblast activation protein (FAP) is a key player in epithelial-to-mesenchymal transition (EMT). However, its clinical value and role in NE differentiation in advanced PC has not been fully investigated. Methods: Two hundred and eight patients from a multicenter, prospective cohort of patients with metastatic castration-resistant prostate cancer (CRPC) with available RNA sequencing data were analyzed for tumor FAP mRNA expression, and its association with overall survival (OS) and NE tumor features was investigated. Results: Twenty-one patients (10%) were found to have high FAP mRNA expression. Compared to the rest, this subset had a proportionally higher exposure to taxanes and AR signaling inhibitors (abiraterone or enzalutamide) and was characterized by active NE signaling, evidenced by high NEPC- and low AR-gene expression scores. These patients with high tumor mRNA FAP expression had a more aggressive clinical course and significantly shorter survival (12 months) compared to those without altered FAP expression (28 months, log-rank p = 0.016). Conclusions: FAP expression may serve as a valuable NE marker indicating a worse prognosis in patients with metastatic CRPC.

The HeyL-Aromatase Axis Promotes Cancer Stem Cell Properties by Endogenous Estrogen-Induced Autophagy in Castration-Resistant Prostate Cancer

Treatment of patients with castration-resistant prostate cancer (CRPC) remains a major clinical challenge. We previously showed that estrogenic effects contribute to CRPC progression and are primarily caused by the increased endogenous estradiol produced via highly expressed aromatase. However, the mechanism of aromatase upregulation and its role in CRPC are poorly described. In this study, we report that HeyL is aberrantly upregulated in CRPC tissues, and its expression is positively correlated with aromatase levels. HeyL overexpression increased endogenous estradiol levels and estrogen receptor-α (ERα) transcriptional activity by upregulating CYP19A1 expression, which encodes aromatase, enhancing prostate cancer stem cell (PCSC) properties in PC3 cells. Mechanistically, HeyL bound to the CYP19A1 promoter and activated its transcription. HeyL overexpression significantly promoted bicalutamide resistance in LNCaP cells, which was reversed by the aromatase inhibitor letrozole. In PC3 cells, the HeyL-aromatase axis promoted the PCSC phenotype by upregulating autophagy-related genes, while the autophagy inhibitor chloroquine (CQ) suppressed the aromatase-induced PCSC phenotype. The activated HeyL-aromatase axis promoted PCSC autophagy via ERα-mediated estrogenic effects. Taken together, our results indicated that the HeyL-aromatase axis could increase endogenous estradiol levels and activate ERα to suppress PCSC apoptosis by promoting autophagy, which enhances the understanding of how endogenous estrogenic effects influence CRPC development.

Incorporating external trial data to improve survival extrapolations: a pilot study of the COU-AA-301 trial

Survival extrapolation plays a key role within cost effectiveness analysis and is often subject to substantial uncertainty. Use of external data to improve extrapolations has been identified as a key research priority. We present findings from a pilot study using data from the COU-AA-301 trial of abiraterone acetate for metastatic castration-resistant prostate cancer, to explore how external trial data may be incorporated into survival extrapolations. External trial data were identified via a targeted search of technology assessment reports. Four methods using external data were compared to simple parametric models (SPMs): informal reference to external data to select appropriate SPMs, piecewise models with, and without, hazard ratio adjustment, and Bayesian models fitted with a prior on the shape parameter(s). Survival and hazard plots were compared, and summary metrics (point estimate accuracy and restricted mean survival time) were calculated. Without consideration of external data, several SPMs may have been selected as the ‘best-fitting’ model. The range of survival probability estimates was generally reduced when external data were included in model estimation, and external hazard plots aided model selection. Different methods yielded varied results, even with the same data source, highlighting potential issues when integrating external trial data within model estimation. By using external trial data, the most (in)appropriate models may be more easily identified. However, benefits of using external data are contingent upon their applicability to the research question, and the choice of method can have a large impact on extrapolations.

Combination therapy for mCRPC with immune checkpoint inhibitors, ADT and vaccine: A mathematical model

Metastatic castration resistant prostate cancer (mCRPC) is commonly treated by androgen deprivation therapy (ADT) in combination with chemotherapy. Immune therapy by checkpoint inhibitors, has become a powerful new tool in the treatment of melanoma and lung cancer, and it is currently being used in clinical trials in other cancers, including mCRPC. However, so far, clinical trials with PD-1 and CTLA-4 inhibitors have been disappointing. In the present paper we develop a mathematical model to assess the efficacy of any combination of ADT with cancer vaccine, PD-1 inhibitor, and CTLA-4 inhibitor. The model is represented by a system of partial differential equations (PDEs) for cells, cytokines and drugs whose density/concentration evolves in time within the tumor. Efficacy of treatment is determined by the reduction in tumor volume at the endpoint of treatment. In mice experiments with ADT and various combinations of PD-1 and CTLA-4 inhibitors, tumor volume at day 30 was always larger than the initial tumor. Our model, however, shows that we can decrease tumor volume with large enough dose; for example, with 10 fold increase in the dose of anti-PD-1, initial tumor volume will decrease by 60%. Although the treatment with ADT in combination with PD-1 inhibitor or CTLA-4 inhibitor has been disappointing in clinical trials, our simulations suggest that, disregarding negative effects, combinations of ADT with checkpoint inhibitors can be effective in reducing tumor volume if larger doses are used. This points to the need for determining the optimal combination and amounts of dose for individual patients.

Enzalutamide in metastatic castration-resistant prostate cancer, real-world data

Objective: Androgen deprivation therapy (ADT) is used alone or in combination with docetaxel or androgen inhibitors in the initial treatment of metastatic prostate cancer (PC) (mPC). Enzalutamide is an androgen receptor inhibitor that is used orally and plays a role in different steps of the androgen receptor (AR) signal pathway. The aim of this study is to determine the real life data of patients using enzalutamide for metastatic PC. Material and Methods: The 118 patients from a totally 6 centers using enzalutamide treatment were included in this retrospective analysis. Clinical information of patients was recorded from patient files or automation records. Results: Median OS was 71 months, and median PFS was five months (4,1 – 5,9 months). There was no association of Gleason score with OS and PFS (p = 0.5 and p = 0.4, respectively). Although those who were metastatic at the time of diagnosis lived longer than those who developed metastases later, the difference was not statistically significant (p = 0.9). Likewise, there was no relationship between the time of metastasis development and PFS (p = 0.2). There was no difference in OS and PFS between patients with visceral metastasis and those without (p = 0.3, p = 0.5, respectively). Conclusion: Enzalutamide is an effective and safe agent in accordance with the literature in the patient group included in this study, although some patients may have an unresponsiveness to enzalutamide or develop progression under the enzalutamide treatment. More studies are needed to understand which patient group can benefit more from enzalutamide.

Drug Repurposing of Asparaginase and Vitamin C Targeting Glutamine Synthetase Improves Anticancer Effect in Metastatic Castration-resistant Prostate Cancer

Background: Although in North America or Europe early dignosis of prostate cancer could sucessfully improves the therapeutic outcome. However, about 70-80% of patients still suffer from metastatic castration-resistant prostate cancer (mCRPC), because of the disproportionate medical care in China. Lutetium-177 (Lu-177) or Radium-223 (Ra-223) has been suggested as the most effective therapy for mCRPC. Unfortunately, they are either not been approved in a few countries or too expensive for patients with the financial issue. Drug repurposing has been recognized as a cost-effective and relatively low-risk alternative, gains a lot interesting recently. In this study, we explored the combined treatment with asparaginase (ASNase) and/or vitamin Cas an alternative therapeutic option for mCRPC management.Methods: Prostate cancer cell lines PC3 and DU145 were used to observe the therapeutic effect of ASNase and/or vitamin C on mCRPC in vitro and in vivo. Change of cell proliferation, cell death as well as expression of glutamine synthetase eunder different treatment conditions were detected to analyzed anticancer effect of combined therapy with ASNase and vitamin C on mCRPC. Intracellular oxidation was also observed with NADPH and NADP+ assay. Male BALB/c nude mice bearing prostate carcinoma xenografts (PC3 or DU145) were used to assess treatment response to vitamin C with or without ASNase through tumor growth, small animal PET/CT scans as well as Immunohistochemistry in vivo.Results: Our in vitro studies demonstrate that ASNase synergizes with vitamin C targeting expression of glutamine synthetase enhances redox imbalance and induces anticancer effect in mCRPC cells through regulation the glutamine synthetase (GS) expression. In vivo, combination of ASnase and vitamin C could provide a significant better therapeutic outcome in comparison with controls or single treated mice. 18F-FDG PET imaging illustrated that the treatment with combined therapy could significantly reduce the 18F-FDG uptake in tumor.Conclusions: In this current study, we suggest that ASNase combined with vitamin C could be as a cost-effective strategy to manage mCRPC.18F-FDG PET/CT imaging could indicate the therapeutic response of treatment for mCRPC.