TMIC-73. SEX DIFFERENCES IN INTERFERON-GAMMA RESPONSES IN GLIOMA MICROENVIRONMENT

Abstract IFNγ is a cytokine with both pro- and anti-tumorigenic effects and its role in glioma immunotherapy resistance is not well understood. In the tumor microenvironment, T and NK cells produce IFNγ, which affects cellular phenotypes in most of the cancer and stromal cells since IFNγ receptor is ubiquitously expressed. IFNγ induces expression of molecules that confer resistance to immunotherapies, such as PDL1, PDL2, IDO1, and iNOS. The goal of this study is to elucidate cell type-specific responses to IFNγ in immune competent glioma models we developed that are resistant to immunotherapy. We intracranially injected male and female murine glioma cells into B6 and Ifng-/- honst mice to measure overall survival and perform immune phenotyping and single cell RNA-sequencing analyses. Ifnγ-/- hosts exhibited a shorter survival, and the proportion of GBM cells is higher in Ifng-/- hosts compared to wild type, indicating that the net effect of IFNγ signaling in glioma is anti-tumorigenic. In a recent study, we published that IFNγ-response pathway is enriched in the mesenchymal-like (MES-like) subtype of human GBM cells, compared to neutral-progenitor-like (NPC-like) and oligodendrocyte-progenitor-like (OPC-like) cells (Abdelfattah et al., 2022). To test our hypothesis that IFNγ signaling induces MES transition in glioma cells in vivo, we compared fractions of glioma cell subtypes in wildtype and Ifng-/- male and female hosts. In female Ifng-/- mice, MES-like GBM cell fraction was reduced while OPC-like fraction was increased, supporting our hypothesis. However, there was no difference in male hosts. Furthermore, gliomas grown in female B6 hosts showed higher infiltration of immune cells (CD45+), lymphocytes (CD3+) and fewer resident microglia cells (CD11b+CD45int), compared with Ifng-/- female hosts. In contrast, no significant difference in immune cell infiltration was observed between B6 vs Ifng-/- males. These results suggest an unanticipated and complex context-dependent role of IFNγ signaling in GBM, which include sex differences in its role in immune cell recruitment and MES transition in glioma cells.