Biomarker-based targeting of the androgen-androgen receptor axis in advanced prostate cancer

Molecular Phenotyping of AR Signaling for Predicting Targeted Therapy in Castration Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPC) is defined by resistance of the tumor to androgen deprivation therapy (ADT). Several molecular changes, particularly in the AR signaling cascade, have been described that may explain ADT resistance. The variety of changes may also explain why the response to novel therapies varies between patients. Testing the specific molecular changes may be a major step towards personalized treatment of CRPC patients. The aim of our study was to evaluate the molecular changes in the AR signaling cascade in CRPC patients. We have developed and validated several methods which are easy to use, and require little tissue material, for exploring AR signaling pathway changes simultaneously. We found that the AR signaling pathway is still active in the majority of our CRPC patients, due to molecular changes in AR signaling components. There was heterogeneity in the molecular changes observed, but we could classify the patients into 4 major subgroups which are: AR mutation, AR amplification, active intratumoral steroidogenesis, and combination of AR amplification and active intratumoral steroidogenesis. We suggest characterizing the AR signaling pathway in CRPC patients before beginning any new treatment, and a recent fresh tissue sample from the prostate or a metastatic site should be obtained for the purpose of this characterization.

Systematic identification of functionally relevant risk alleles to stratify aggressive versus indolent prostate cancer

Novel approaches for classification, including molecular features, are needed to direct therapy for men with low-grade prostate cancer (PCa), especially men on active surveillance. Risk alleles identified from genome-wide association studies (GWAS) could improve prognostication. Those risk alleles that coincided with genes and somatic copy number aberrations associated with progression of PCa were selected as the most relevant for prognostication.

In a systematic literature review, a total of 698 studies were collated. Fifty-three unique SNPs residing in 29 genomic regions, including 8q24, 10q11 and 19q13, were associated with PCa progression. Functional studies implicated 21 of these single nucleotide polymorphisms (SNPs) as modulating the expression of genes in the androgen receptor pathway and several other oncogenes. In particular, 8q24, encompassing MYC, harbours a high density of SNPs conferring unfavourable pathological characteristics in low-grade PCa, while a copy number gain of MYC in low-grade PCa was associated with prostate-specific antigen recurrence after radical prostatectomy.

By combining GWAS data with gene expression and structural rearrangements, risk alleles were identified that could provide a new basis for developing a prognostication tool to guide therapy for men with early prostate cancer.

A comprehensive review of genomic landscape, biomarkers and treatment sequencing in castration-resistant prostate cancer

Hormone-naïve prostate cancer and its castration-resistant state (CRPC) are clinically and genetically heterogeneous diseases. From initiation of prostate carcinogenesis to its evolution towards therapeutic resistance, various combinations of genetic and epigenetic events occur. Schematically, progression to CRPC could be divided in two distinct pathways, either dependent or independent of the androgen receptor activity. Nevertheless, because the better knowledge of the genetic landscape of CRPC is under way, limited clinical applications are available at the moment, underlying the usefulness of prognostic and predictive biomarkers in daily practice. Despite the promising prognostic value of circulating tumor cells, no biomarker has been currently validated as a surrogate for overall survival in CRPC patients. Inversely, considerable interest has been generated with the recent finding of the splice variant AR-V7 that allows to predict resistance to abiraterone acetate and enzalutamide. However, other predictive biomarkers would be necessary to accurately guide personalized sequencing of CRPC treatment, which now includes numerous possibilities based on the six validated drugs, without accounting for those currently under investigation in the ongoing randomized controlled trials. As a consequence, only rational sequencing, which consists in choosing an agent that is not expected to have cross-resistance with previous therapy, can be currently advised.

Mechanistic Insights into Molecular Targeting and Combined Modality Therapy for Aggressive, Localized Prostate Cancer

Radiation therapy (RT) is one of the mainstay treatments for prostate cancer (PCa). The potentially curative approaches can provide satisfactory results for many patients with non-metastatic PCa; however, a considerable number of individuals may present disease recurrence and die from the disease. Exploiting the rich molecular biology of PCa will provide insights into how the most resistant tumor cells can be eradicated to improve treatment outcomes. Important for this biology-driven individualized treatment is a robust selection procedure. The development of predictive biomarkers for RT efficacy is therefore of utmost importance for a clinically exploitable strategy to achieve tumor-specific radiosensitization. This review highlights the current status and possible opportunities in the modulation of four key processes to enhance radiation response in PCa by targeting the: (1) androgen signaling pathway; (2) hypoxic tumor cells and regions; (3) DNA damage response (DDR) pathway; and (4) abnormal extra-/intracell signaling pathways. In addition, we discuss how and which patients should be selected for biomarker-based clinical trials exploiting and validating these targeted treatment strategies with precision RT to improve cure rates in non-indolent, localized PCa.

The emergence of extracellular vesicles in urology: fertility, cancer, biomarkers and targeted pharmacotherapy

Extracellular vesicles (EV) are small membrane-bound vesicles enriched in a selective repertoire of mRNA, miRNA, proteins and cell surface receptors from parental cells and are actively involved in the transmission of inter and intracellular signals. Cancer cells produce EV that contain cargo including DNA, mRNA, miRNA and proteins that allow EV to create epigenetic changes in target cells both locally and systemically. Cancer-derived EV play critical roles in tumorigenesis, cancer cell migration, metastasis, evasion of host immune defense, chemoresistance, and they promote a premetastatic niche favourable to micrometastatic seeding. Their unique molecular profiles acquired from originator cells and their presence in numerous body fluids, including blood and urine, make them promising candidates as biomarkers for prostate, renal and bladder cancers. EV may ultimately serve as targets for therapy and as platforms for personalized medicine in urology. As urologic malignancy comprises 28% of new solid tumour diagnoses and 15% of cancer-related deaths, EV-related research is rapidly emerging and providing unique insights into disease progression. In this report, we review the current literature on EV in the setting of genitourinary fertility and malignancy.

Synergistic action of image-guided radiotherapy and androgen deprivation therapy

The combined use of androgen deprivation therapy (ADT) and image-guided radiotherapy (IGRT) can improve overall survival in aggressive, localized prostate cancer. However, owing to the adverse effects of prolonged ADT, it is imperative to identify the patients who would benefit from this combined-modality therapy relative to the use of IGRT alone. Opportunities exist for more personalized approaches in treating aggressive, locally advanced prostate cancer. Biomarkers--such as disseminated tumour cells, circulating tumour cells, genomic signatures and molecular imaging techniques--could identify the patients who are at greatest risk for systemic metastases and who would benefit from the addition of systemic ADT. By contrast, when biomarkers of systemic disease are not present, treatment could proceed using local IGRT alone. The choice of drug, treatment duration and timing of ADT relative to IGRT could be predicated on these personalized approaches to prostate cancer medicine. These novel treatment intensification and reduction strategies could result in improved prostate-cancer-specific survival and overall survival, without incurring the added expense of metabolic syndrome and other adverse effects of ADT in all patients.

Evolving landscape and novel treatments in metastatic castrate-resistant prostate cancer

Treatment options for castrate-resistant prostate cancer (CRPC) have advanced in recent years and significantly improved the outlook for patients with this aggressive and lethal disease. Further understanding of the biology of CRPC has led to several new targeted therapies and continues to emphasize the importance of androgen receptor (AR) directed therapy. The treatment landscape is rapidly changing and further biologically rationale, biomarker-based ongoing clinical trials are needed. We review the recent results of major clinical trials in CRPC. New and investigational agents now in clinical evaluation are reviewed including inhibitors of angiogenesis, microtubules, chaperones, AR and intracellular kinases, as well as immunotherapy, radiopharmaceuticals and bone-targeted agents. The recent improvement in prognosis for CRPC brings continued optimism for further improvements. Thoughtful planning of clinical trials and further understanding of the mechanisms of resistance to therapies will allow for continued progress in patient care.

Enzalutamide for the treatment of prostate cancer

INTRODUCTION

The FDA approval of docetaxel for metastatic castration-resistant prostate cancer (mCRPC) in 2005 marked a major milestone, as it was the first approved agent for this disease that demonstrated a survival advantage in Phase III assessment of this disease. Since 2009, several other agents have been approved by FDA, including sipuleucel-T, abiraterone, cabazitaxel and enzalutamide . Enzalutamide, a potent antiandrogen that blocks nuclear translocation of the androgen receptor (AR), is the most recently approved of these agents.

AREAS COVERED

The clinical development of enzalutamide is discussed, with attention given as to how this agent will most appropriately be used among a growing list of agents for mCRPC. A MEDLINE search was conducted to identify all relevant published datasets pertaining to the drug. In addition, relevant ASCO and ESMO abstracts were searched.

EXPERT OPINION

The current role and sequencing of enzalutamide may change drastically based on studies such as PREVAIL (a Phase III pre-chemotherapy assessment of enzalutamide) and planned studies to assess relevant combinations (i.e., enzalutamide with abiraterone). Outside of clinical efficacy, issues such as drug cost may ultimately dictate our utilization of agents such as enzalutamide for mCPRC. Although the development of biomarkers to guide therapy for mCRPC is ideal, there are inherent challenges in establishing biomarker-driven treatment.