Combined prostate cancer vaccine plus immune checkpoint inhibition synergizes to eliminate prostate cancer

Area of Science:

• Oncology
• Immunology
• Vaccinology

Background:

• Immunotherapy has shown promise in various cancers, but its efficacy in prostate cancer remains limited.
• Prostate cancer often exhibits resistance to current immunotherapeutic approaches.

Purpose of the Study:

• To evaluate the efficacy of an adenovirus-based bivalent prostate cancer vaccine (Ad-PS2) in combination with immune checkpoint blockade.
• To investigate the synergistic potential of combining dual antigen-targeted vaccination with anti-CTLA4 or anti-PD1 therapy.

Main Methods:

• Utilized immunocompetent mouse models of prostate cancer.
• Administered Ad-PS2 vaccine alone or in combination with low-dose anti-CTLA4 or anti-PD1 antibodies.
• Assessed anti-tumor immunity, tumor elimination, and immune cell infiltration (CD8+ T cells).

Main Results:

• Ad-PS2 combined with anti-CTLA4 demonstrated robust anti-tumor immunity, leading to the elimination of established tumors.
• This combination therapy significantly outperformed monotherapy with either the vaccine or anti-CTLA4.
• Tumor-free mice exhibited durable immune protection against subsequent tumor rechallenge.
• Significant increase in intratumor CD8+ T cell infiltration was observed with the Ad-PS2 and anti-CTLA4 combination.
• Anti-PD1 therapy, alone or with the vaccine, showed minimal therapeutic advantage and limited T cell infiltration.

Conclusions:

• A synergistic interaction exists between dual antigen-targeted vaccination and CTLA4 blockade in prostate cancer.
• Rational combination immunotherapy strategies can overcome resistance in prostate cancer.
• This approach may inform future translational strategies for enhancing immunologic control of prostate cancer.