Androgen receptor (AR) in prostate cancer (PCa) can drive transcriptional repression of multiple genes including MYC, and supraphysiological androgen is effective in some patients. Here, we show that this repression is independent of AR chromatin binding and driven by coactivator redistribution, and through chromatin conformation capture methods show disruption of the interaction between the MYC super-enhancer within the PCAT1 gene and the MYC promoter. Conversely, androgen deprivation in vitro and in vivo increases MYC expression. In parallel, global AR activity is suppressed by MYC overexpression, consistent with coactivator redistribution. These suppressive effects of AR and MYC are mitigated at shared AR/MYC binding sites, which also have markedly higher levels of H3K27 acetylation, indicating enrichment for functional enhancers. These findings demonstrate an intricate balance between AR and MYC, and indicate that increased MYC in response to androgen deprivation contributes to castration-resistant PCa, while decreased MYC may contribute to responses to supraphysiological androgen therapy.

PurposeTo systematically evaluate the overall efficacy and safety of current anti-PD-1/PD-L1 antibodies for treatment of patients with advanced or refractory cancer.ResultsFifty-one trials including 6,800 patients were included. The overall response rates for melanoma, non-small cell lung cancer (NSCLC), and renal cell carcinoma (RCC) were 29% (95% CI: 1.53−2.41), 21% (95% CI: 17%−25%) and 21% (95% CI: 16%−27%) respectively. While the overall adverse effects rate for melanoma, NSCLC, RCC were 16% (95% CI: 6%−28%), 11% (95% CI: 8%−14%) and 20% (95% CI: 11%−32%) respectively. Tumor PD-L1 expression and patient smoking status might serve as biomarkers to predict response of anti-PD-1/PD-L1 antibody treatment. Compared to tumors with negative PD-L1 expression, tumors with positive PD-L1 expression had a significantly higher clinical response rate (41.4% versus 26.5%) with RR = 1.92 (95% CI: 1.53−2.41, P < 0.001). Smoker patients also showed a significantly higher response rate (33.7%) than patients who never smoked (4.2%) with RR = 6.02 (95% CI: 1.22−29.75, P = 0.028). Nivolumab and Pembrolizumab were associated with significantly increased response rate (RR = 2.89, 95% CI: 2.46−3.40, P < 0.001), reduced death risk (HR= 0.53; 95% CI: 0.48−0.57; P < 0.001), and decreased adverse effect rate (RR = 0.49, 95% CI: 0.30−0.80, P = 0.004) compared with other therapies.Experimental DesignClinical trials reporting response or safety of anti-PD-1/PD-L1 antibodies for advanced or refractory cancer patients published before January 31th 2016 were searched in PubMed and EMBASE database. Meta-analyses using random effects models were used to calculate the overall estimate.ConclusionsAnti-PD-1/PD-L1 antibodies have high response rates and low adverse effect rates for advanced or refractory cancers.

The standard treatment for metastatic prostate cancer (PCa), androgen deprivation therapy (ADT), is designed to suppress androgen receptor (AR) activity. However, men invariably progress to castration-resistant prostate cancer (CRPC), and AR reactivation contributes to progression in most cases. To identify mechanisms that may drive CRPC, we examined a VCaP PCa xenograft model as tumors progressed from initial androgen sensitivity prior to castration to castration resistance and then on to relapse after combined therapy with further AR targeted drugs (abiraterone plus enzalutamide). AR activity persisted in castration-resistant and abiraterone/enzalutamide-resistant xenografts and was associated with increased expression of the AR gene and the AR-V7 splice variant. We then assessed expression of individual AR-regulated genes to identify those that persisted, thereby contributing to tumor growth, versus those that decreased and may therefore exhibit tumor suppressor activities. The most significantly decreased AR target gene was Dipeptidyl Peptidase 4 (DPP4), which encodes a membrane-anchored protein that cleaves dipeptides from multiple growth factors, resulting in their increased degradation. DPP4 mRNA and protein were also decreased in clinical CRPC cases, and inhibition of DPP4 with sitagliptin enhanced the growth of PCa xenografts following castration. Significantly, DPP4 inhibitors are frequently used to treat type 2 diabetes as they increase insulin secretion. Together these results implicate DPP4 as an AR-regulated tumor suppressor gene whose loss enhances growth factor activity and suggest that treatment with DPP4 inhibitors may accelerate emergence of resistance to ADT.

Clinically available BH3 mimetic drugs targeting BCLXL and/or BCL2 (navitoclax and venetoclax, respectively) are effective in some hematologic malignancies, but have limited efficacy in solid tumors. This study aimed to identify combination therapies that exploit clinical BH3 mimetics for prostate cancer. Prostate cancer cells or xenografts were treated with BH3 mimetics as single agents or in combination with other agents, and effects on MCL1 and apoptosis were assessed. MCL1 was also targeted directly using RNAi, CRISPR, or an MCL1-specific BH3 mimetic, S63845. We initially found that MCL1 depletion or inhibition markedly sensitized prostate cancer cells to apoptosis mediated by navitoclax, but not venetoclax, and, indicating that they are primed to undergo apoptosis and protected by MCL1 and BCLXL. Small-molecule EGFR kinase inhibitors (erlotinib, lapatinib) also dramatically sensitized to navitoclax-mediated apoptosis, and this was associated with markedly increased proteasome-dependent degradation of MCL1. This increased MCL1 degradation appeared to be through a novel mechanism, as it was not dependent upon GSK3β-mediated phosphorylation and subsequent ubiquitylation by the ubiquitin ligases βTRCP and FBW7, or through other previously identified MCL1 ubiquitin ligases or deubiquitinases. Inhibitors targeting additional kinases (cabozantinib and sorafenib) similarly caused GSK3β-independent MCL1 degradation, and in combination with navitoclax drove apoptosis and These results show that prostate cancer cells are primed to undergo apoptosis and that cotargeting BCLXL and MCL1, directly or indirectly through agents that increase MCL1 degradation, can induce dramatic apoptotic responses..

MCL1 has critical antiapoptotic functions and its levels are tightly regulated by ubiquitylation and degradation, but mechanisms that drive this degradation, particularly in solid tumors, remain to be established. We show here in prostate cancer cells that increased NOXA, mediated by kinase inhibitor activation of an integrated stress response, drives the degradation of MCL1, and identify the mitochondria-associated ubiquitin ligase MARCH5 as the primary mediator of this NOXA-dependent MCL1 degradation. Therapies that enhance MARCH5-mediated MCL1 degradation markedly enhance apoptosis in response to a BH3 mimetic agent targeting BCLXL, which may provide for a broadly effective therapy in solid tumors. Conversely, increased MCL1 in response to MARCH5 loss does not strongly sensitize to BH3 mimetic drugs targeting MCL1, but instead also sensitizes to BCLXL inhibition, revealing a codependence between MARCH5 and MCL1 that may also be exploited in tumors with MARCH5 genomic loss.

Differences in the incidence and mortality rate of prostate cancer between the USA and Japan have been decreasing over time, and were only twofold in 2017. Therefore, countermeasures against prostate cancer could be very important not only in Western countries, but also in developed Asian countries. Screening for prostate cancer in the general population using transrectal ultrasonography, digital rectal examination and/or prostate acid phosphatase began in Japan in the early 1980s, and screening with prostate‐specific antigen and digital rectal examination has been widespread in the USA since the late 1980s. Large‐ and mid‐scale randomized controlled trials on screening for prostate cancer began around 1990 in the USA, Canada and Europe. However, most of these studies failed as randomized controlled trials because of high contamination in the control arm, low compliance in the screening arm or insufficient screening setting about screening frequency and/or biopsy indication. The best available level 1 evidence is data from the European Randomized Study of Screening for Prostate Cancer and the Göteborg screening study. However, several non‐urological organizations and lay media around the world have mischaracterized the efficacy of prostate‐specific antigen screening. To avoid long‐term confusion about screening for prostate cancer, leading professional urological organizations, including the Japanese Urological Association, are moving toward the establishment of an optimal screening system that minimizes the drawbacks of overdetection, overtreatment and loss of quality of life due to treatment, and maximizes reductions in the risk of death as a result of prostate cancer and the development of metastatic prostate cancer.

Purpose of review: Prostate cancer is diagnosed in one out of every nine men and is the second leading cause of cancer death among men. While therapies targeting the androgen receptor are highly effective, development of resistance is universal and remains a major therapeutic challenge. Nonetheless, signaling via androgen receptor is frequently maintained despite standard androgen signaling inhibition. We review the current understanding of mechanisms of resistance as well as therapeutic approaches to improving treatment of prostate cancer via targeting of the androgen receptor. Recent findings: Resistance to androgen-receptor-targeting therapies may be mediated by several mechanisms, including amplification, mutation, and alternative splicing of androgen receptor; intratumoral androgen synthesis; activation of alternative signaling pathways; and in a minority of cases, emergence of androgen-receptor-independent phenotypes. Recent trials demonstrate that intensification of androgen blockade in metastatic castration-sensitive prostate cancer can significantly improve survival. Similar strategies are being explored in earlier disease states. In addition, several other cellular signaling pathways have been identified as mechanisms of resistance, offering opportunities for co-targeted therapy. Finally, immune-based approaches are in development to complement androgen-receptor-targeted therapies.

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