Biological response determinants in HSV-tk + ganciclovir gene therapy for prostate cancer

Area of Science:

• Oncology
• Gene Therapy
• Immunotherapy

Background:

• Current prostate cancer therapies have limitations, necessitating novel treatment strategies.
• Previous research indicated a cytopathic effect of Herpes Simplex Virus-thymidine kinase (HSV-tk) in prostate cancer.
• A need exists to explore neoadjuvant gene therapy for localized prostate cancer with high recurrence risk.

Purpose of the Study:

• To evaluate the initial safety and efficacy of neoadjuvant HSV-tk gene therapy in men with localized prostate cancer.
• To investigate the mechanistic aspects of HSV-tk gene therapy's effects in human prostate tissues.
• To assess the impact of HSV-tk gene therapy on tumor characteristics, immune response, apoptosis, and angiogenesis.

Main Methods:

• A Phase I-II clinical trial involving 23 men with localized prostate cancer at high risk for recurrence.
• Intraprostatic viral injections of HSV-tk followed by ganciclovir administration.
• Surgical specimen analysis using whole-mount slides to evaluate cytopathic effects, immune cell infiltration, apoptosis, and microvessel density.

Main Results:

• The neoadjuvant HSV-tk gene therapy exhibited modest toxicity.
• A greater cytopathic effect was observed in larger tumors and correlated with high Coxsackie and Adenovirus Receptor (CAR) expression.
• Treatment increased local and systemic immune responses (CD8+ cells, macrophages, IL-12), elevated apoptosis, and decreased microvessel density.

Conclusions:

• Neoadjuvant HSV-tk gene therapy demonstrates a tumor-specific effect in prostate cancer.
• The therapy's efficacy appears mediated by a combination of systemic and local immune responses, antiangiogenic effects, and apoptosis modulation.
• These findings support HSV-tk gene therapy as a potential novel therapeutic approach for prostate cancer.