Abcc3 Up-Regulation Confers Protection From Chemotherapy To Nk Cells In A Murine Model Of Malignant Glioma

Growing evidence suggests that chemotherapy can influence the immune response by inducing lymphopenia or enhancing immunogenicity of dying tumor cells. In a clinical trial currently active in our Institution, patients with first diagnosis of glioblastoma are treated with dendritic cells (DC) loaded with autologous tumor lysate together with standard radio and chemotherapy with temozolomide. Peripheral blood lymphocytes from 22 patients were analyzed by flow cytometry to identify immune cell activation before and after DC vaccines. The ratio of vaccine/baseline frequencies (V/B ratio) was correlated with the survival of each patient. Increased V/B ratio for NK cells was significantly associated with prolonged PFS and OS (median 15.0 vs 8.0 mo, p = 0.003; 22.0 vs 12.0 mo, p = 0.02, respectively). Using the murine malignant glioma GL261, we investigated the molecular mechanisms induced by TMZ on NK and CD8 T cells. We treated mice 9 days after intracranial implantation of GL261 cells with intraperitoneal injections of TMZ (5 mg/kg) or vehicle (control mice) for 5 days. Mice were sacrificed at different time points and tumor and peripheral blood harvested and analyzed by flow cytometry. Gene expression profiling on peripheral blood lymphocytes revealed an up-regulation of multidrug resistance genes in NK cells, but not in CD8 T lymphocytes, in TMZ-treated mice compared to controls. The increased expression of the ATP transporter gene Abcc3 was confirmed by real time PCR (4.2-fold higher than controls, P = 0.006). Using eFluxx-ID multidrug resistance (MDR) assay based on specific inhibitors, we also demonstrated that Abcc3 was functionally active during TMZ treatment. NK cell resistance to chemotherapy was accompanied by an increase in migration and homing ability into the brain at early time point and in cytotoxicity at later phases (beyond the end of TMZ treatment). Our data show that murine NK cells are resistant to and activated by TMZ chemotherapy. Further investigations in patients treated by radio-chemotherapy with or without DC immunotherapy are warranted. Note: This abstract was not presented at the meeting. Citation Format: Serena Pellegatta, Sara Pessina, Gabriele Cantini, Emanuela Cazzato, Dimos Kapetis, Gaetano Finocchiaro. Abcc3 up-regulation confers protection from chemotherapy to NK cells in a murine model of malignant glioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1343. doi:10.1158/1538-7445.AM2015-1343