Horizon scanning for novel therapeutics for the treatment of prostate cancer

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.

Androgen receptor-dependent and -independent mechanisms driving prostate cancer progression: Opportunities for therapeutic targeting from multiple angles

Despite aggressive treatment for localized cancer, prostate cancer (PC) remains a leading cause of cancer-related death for American men due to a subset of patients progressing to lethal and incurable metastatic castrate-resistant prostate cancer (CRPC). Organ-confined PC is treated by surgery or radiation with or without androgen deprivation therapy (ADT), while options for locally advanced and disseminated PC include radiation combined with ADT, or systemic treatments including chemotherapy. Progression to CRPC results from failure of ADT, which targets the androgen receptor (AR) signaling axis and inhibits AR-driven proliferation and survival pathways. The exact mechanisms underlying the transition from androgen-dependent PC to CRPC remain incompletely understood. Reactivation of AR has been shown to occur in CRPC despite depletion of circulating androgens by ADT. At the same time, the presence of AR-negative cell populations in CRPC has also been identified. While AR signaling has been proposed as the primary driver of CRPC, AR-independent signaling pathways may represent additional mechanisms underlying CRPC progression. Identification of new therapeutic strategies to target both AR-positive and AR-negative PC cell populations and, thereby, AR-driven as well as non-AR-driven PC cell growth and survival mechanisms would provide a two-pronged approach to eliminate CRPC cells with potential for synthetic lethality. In this review, we provide an overview of AR-dependent and AR-independent molecular mechanisms which drive CRPC, with special emphasis on the role of the Jak2-Stat5a/b signaling pathway in promoting castrate-resistant growth of PC through both AR-dependent and AR-independent mechanisms.

The changing therapeutic landscape of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) has a poor prognosis and remains a significant therapeutic challenge. Before 2010, only docetaxel-based chemotherapy improved survival in patients with CRPC compared with mitoxantrone. Our improved understanding of the underlying biology of CRPC has heralded a new era in molecular anticancer drug development, with a myriad of novel anticancer drugs for CRPC entering the clinic. These include the novel taxane cabazitaxel, the vaccine sipuleucel-T, the CYP17 inhibitor abiraterone, the novel androgen-receptor antagonist MDV-3100 and the radioisotope alpharadin. With these developments, the management of patients with CRPC is changing. In this Review, we discuss these promising therapies along with other novel agents that are demonstrating early signs of activity in CRPC. We propose a treatment pathway for patients with CRPC and consider strategies to optimize the use of these agents, including the incorporation of predictive and intermediate end point biomarkers, such as circulating tumor cells.