Gene therapy for prostate cancer: Current status and future prospects

Purpose: Locally advanced, relapsed and metastatic prostate cancer has a di smal prognosis with conventional therapies offering no more than palliation . In recent years advances achieved in understanding the molecular biology of cancer have afforded clinicians and scientists the opportunity to develo p a range of novel genetic therapies for this disease. Materials and Methods: We performed a detailed review of published reports of gene therapy for prostate cancer. Particular emphasis was placed on rece nt developments in the arena of nonviral (plasmid DNA, DNA coated gold part icles, liposomes and polymer DNA complexes) and viral (adenovirus, retrovir us, adeno-associated virus, herpes virus and pox virus) vectors. Therapeuti c strategies were categorized as corrective, cytoreductive and immunomodula tory gene therapy for the purpose of data analysis and comparison. Results: Locoregional administration of nonviral and viral vectors can yiel d impressive local gene expression and therapeutic effects but to our knowl edge no efficient systemically delivered vector is available to date. Corre ctive gene therapy to restore normal patterns of tumor suppressor gene (p53 , Rb, p21 and p16) expression or negate the effect of mutated tumor promoti ng oncogenes (ras, myc, erbB2 and bcl-2) have efficacy in animal models but this approach suffers from the fact that each cancer cell must be targeted . A wide variety of cytoreductive strategies are under development, includi ng suicide, anti-angiogenic, radioisotopic and pro-apoptotic gene therapies . Each approach has strengths and weaknesses, and may best be suited for us e in combination. Immunomodulatory gene therapy seeks to generate an effect ive local immune response that translates to systemic antitumor activity. C urrently most studies involve immunostimulatory cytokine genes, such as gra nulocyte-macrophage colony-stimulating factor, or interleukin-2 or 12. Conclusions: Various therapeutic genes have proved activity against prostat e cancer in vitro and in vivo. However, the chief challenge facing clinical gene therapy strategies is the lack of efficient gene delivery by local an d systemic routes. For the foreseeable future vector development may remain a major focus of ongoing research. Despite this caveat it is anticipated t hat gene therapy approaches may significantly contribute to the management of prostate cancer in the future.