Abstract A60: NK cell activation and cytotoxicity can be enhanced with chemotherapy in a murine model of glioblastoma.

Chemotherapy is currently regarded as a potential ally for cancer immunotherapy. Several anticancer agents, including classical chemotherapeutic compounds, are able to enforce tumor specific immune responses either by inducing the immunogenic death of tumor cells or by modulating key cells for immune suppression or activation. To determine whether Temozolomide (TMZ), the standard chemotherapeutic agent for glioblastoma and malignant gliomas, could induce tumor immunogenicity, we treated murine GL261 cells with 50 and 150 microM TMZ in vitro for 2, 8 and 20 hours. Flow cytometry showed that the NKG2D ligand, involved in NKG2D-mediated NK cell recognition of tumor cells, was highly expressed by TMZ-treated GL261, whereas GL261 treated with vehicle showed only a weak expression (P We therefore studied the effects of TMZ on anti-tumor NK cell response by treating mice 7 days after intracranial implantation of GL261 gliomas with intraperitoneal injections of TMZ (5mg/kg) or vehicle (control mice) for 5 days. Five mice were sacrificed 20 hours after treatment on days 1-5: brain, spleen and blood were harvested and analyzed by flow cytometry. Trafficking of NKp46+ NK1.1+ CD3- NK cells in blood but not in spleen and their homing ability into the brain significantly increased in TMZ-treated compared to control mice after the second administration of TMZ (7.5 ± 1.4 vs 2.3 ± 1.2, P = 0.001; 10.9 ± 0.4 vs. 3.9 ± 0.6, P = 0.005, respectively). Notably TMZ led to an enrichment of CD11bhigh CD27high NK cells, the most potent effector cells. To verify NK anti-glioma activity, NK1.1 positive cells were isolated from blood and brain of treated and control mice using magnetic separation and incubated with GL261 cells. NK cell cytotoxicity from TMZ-treated mice was significantly higher than that NK cells from control mice. These results support the contention that chemotherapy may induce enhancement of NK cell response and open new opportunities to design novel combined therapies reversing the immune suppressive role of glioblastoma and unmasking the therapeutic potential of NK responses. Citation Format: Serena Pellegatta, Gabriele Cantini, Sara Pessina, Gaetano Finocchiaro. NK cell activation and cytotoxicity can be enhanced with chemotherapy in a murine model of glioblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A60.