Pathology and molecular updates in tumors of the prostate: towards a personalized approach

INTRODUCTION

Treatment planning in patients with prostate neoplasms and prostate cancer (PCa) is generally based on the clinical and pathological molecular markers obtained from prostate needle biopsy and/or radical prostatectomy specimens. Area covered: Pathology of prostate neoplasms is evolving rapidly. Emerging trends include new additions to the 2016 World Health Organization (WHO) tumor classification as well as expanded diagnostic utility of biomarkers and molecular testing in tissue specimens, liquid biopsies and urinary samples, with the following purposes: diagnosis, prognosis and prediction. Expert commentary: The new additions to the 2016 WHO tumor classification, which include pathological definition of Intraductal carcinoma of the prostate (IDC-P) and of a new grading system for PCa, as well as identification of molecular markers, such as TMPRSS2-ERG and AR-V7, may pave the way to personalized therapy for patients with prostate tumors.

AR-V7 and prostate cancer: The watershed for treatment selection?

The androgen receptor (AR) plays a key role in progression to metastatic castration-resistant prostate cancer (mCRPC). Despite the recent progress in targeting persistent AR activity with the next-generation hormonal therapies (abiraterone acetate and enzalutamide), resistance to these agents limits therapeutic efficacy for many patients. Several explanations for response and/or resistance to abiraterone acetate and enzalutamide are emerging, but growing interest is focusing on importance of AR splice variants (AR-Vs) and in particular of AR-V7. Increasing evidences highlight the concept that variant expression could be used as a potential predictive biomarker and a therapeutic target in advanced prostate cancer. Therefore, understanding the mechanisms of treatment resistance or sensitivity can help to achieve a more effective management of mCRPC, increasing clinical outcomes and representing a promising and engaging area of prostate cancer research.

Persistent androgen receptor addiction in castration-resistant prostate cancer

It is now understood that persistent activation of the androgen receptor (AR) signaling pathway often underlies the development of castration-resistant prostate cancer (CRPC). This realization led to renewed interest in targeting the AR and ultimately to the development of the potent next-generation AR-directed agents abiraterone and enzalutamide. While these drugs prolong survival in men with CRPC, they are unfortunately not curative. Perhaps not surprisingly, evidence points to persistent AR signaling as one of the key drivers by which resistances to these agents develops. In this context, activation of the AR signaling program can occur through a number of molecular adaptations, including alterations leading to persistent canonical AR signaling (e.g., AR amplification/overexpression, elucidations/concentration of intratumoral androgens), activation of the AR program via feedback pathways (e.g., AKT/mTOR/Pi3K, HER2/Neu), and activation of the AR program via mutation or substitution (e.g., AR ligand binding domain mutation; AR splice variants; glucocorticoid receptor signaling). This review will provide an overview of the more clinical relevant (i.e., druggable) pathways that have been implicated in the emergence of drug resistance in men with CRPC and highlight some of the ongoing efforts towards developing therapeutics to impair these mechanisms.