Targeting the tumor microenvironment in genitourinary cancers: current progress and future directions in prostate cancer

INTRODUCTION: Prostate cancer is no longer considered a 'cold' tumor; several novel immune platforms are now capable of overcoming obstructive cellular and soluble impediments within the tumor microenvironment (TME) thus fostering entry of immune effector cells. Anti-tumor responses are supported by favorable changes in conventional and molecular imaging and the serum biomarker, prostate specific antigen (PSA). AREAS COVERED: This review briefly outlines the current promising strategies with multi-specific antibodies such as T cell engagers, and adoptive cellular therapeutics with chimeric antigen receptor T cells that have successfully gained entry into the tumor microenvironment and generated innate and adaptive immune responses in this disease. These results provide ongoing impetus to pursue immunotherapies in solid tumors, especially those not thought to be enriched with immune cells. EXPERT OPINION: Ongoing research is providing strong evidence that a 'cold' tumor such as metastatic castration resistant prostate cancer (mCRPC) can now respond to unique immunologic constructs. It may be possible to bring these treatments earlier in the disease continuum even as neoadjuvant therapies.