Recombinant oncolytic poliovirus combined with checkpoint blockade for breast cancer therapy.

e12641Background: Breast cancers thrive in an immunosuppressive microenvironment. Checkpoint blockade has had poor results in metastatic breast cancers. Recombinant oncolytic polio:rhinovirus (PVSRIPO) is a novel immunotherapy that infects and kills tumor cells. PVSRIPO enters cells through the CD155 receptor. Triple negative breast cancer (TNBC) tissues express CD155. In the E0771 immunocompetent orthotopic breast cancer murine model, we revealed a single intratumoral PVSRIPO injection significantly delays tumor growth, induces inflammation within the tumor, and stimulates immune cell tumor infiltration. The purpose of our study was to investigate PVSRIPO with checkpoint blockade for breast cancer therapy. Methods: BL6-CD155 transgenic mice were implanted in the mammary fatpad with 1x106 E0771CD155 tumor cells. Mouse PVSRIPO (mRIPO, 5x107 pfu) were injected intratumorally one time when tumors reached 100 mm3. Checkpoint antibodies (250 µg in 200 µL PBS) were injected intraperitoneally the day after PVSRI...