Abstract 721: Opposite roles of CD11b+ myeloid cells in primary and recurrent brain tumors

Abstract

Abstract Malignant glioma is one of the toughest tumors to be treated at present due to the complexity of the tumor microenvironment and the intrinsic resistant to irradiation. Previous studies have shown that CD11b+ myleoid cells play essential role in brain tumor recurrence following radiation therapy. Here we used the CD11b-diphtheria toxin receptor (CD11b-DTR) transgenic mouse model to evaluate the role of CD11b+ myleoid cells in TK/GCV suicide gene therapy for brain tumor in a murine astrocytomal tumor model, ALTS1C1-TK. Using this transgenic mouse model, the depletion of peritoneal macrophages (CD11b+F4/80+) and blood monocyte (CD11b+Ly6G−Ly6c−) could be achieved after two injections of DT, but the neutrophil (CD11b+Gr-1+) were increased transiently. Results found that the depletion of CD11b+ myleoid cells enhanced the efficacy of TK/GCV therapy as shown by the increase of median surviving time of GCV-treated ALTS1C1-TK tumor-bearing mice from 30.6 days to 37.5 days. Interestingly, the depletion of CD11b+ myleoid cells enhanced tumor growth as shown that tumor-bearing mice had shorter surviving days and larger tumor size after receiving two doses of DT injections compared to the control PBS group (22.4 days vs 25.0 days, respectively). This indicates that depleted CD11b+ myleoid cells might have anti-tumor function for control tumor, but have pro-tumor activity during TK/GCV therapy. This study also found the effect of CD11b+ myleoid cells was only seen when the depletion was performed during the administration of GCV, but not before or after GCV treatment. Collectively, above findings suggest that CD11b+ myleoid cells might have different roles on primary and recurrent brain tumors. Citation Format: Wu Sheng-Yen. Opposite roles of CD11b+ myeloid cells in primary and recurrent brain tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 721.