Mast cells modulate proliferation, migration and stemness of glioma cells through downregulation of GSK3β expression and inhibition of STAT3 activation.

Glioblastoma (GBM) heterogeneity is the main obstacle to efficient treatment due to the existence of subpopulation of cells with increased tumorigenicity and network of tumor associated parenchymal cells in the tumor microenvironment. We previously demonstrated that mast cells (MCs) infiltrate mouse and human gliomas in response to variety of signals in a glioma grade-dependent manner. However, the role of MCs in glioma development and the mechanisms behind MCs-glioma cells interaction remain unidentified. In the present study, we show that MCs upon activation by glioma cells produce soluble factors including IL-6, which are documented to be involved in cancer-related activities. We observe 'tumor educated' MCs decrease glioma cell proliferation and migration, reduce self-renewal capacity and expression of stemness markers but in turn promote glioma cell differentiation. 'Tumor educated' MC derived mediators exert these effects via inactivation of STAT3 signaling pathway through GSK3β down-regulation. We identified 'tumor educated' MC derived IL-6 as one of the contributors among the complex mixture of MCs mediators, to be partially involved in the observed MC induced biological effect on glioma cells. Thus, MC mediated abolition of STAT3 signaling hampers glioma cell proliferation and migration by suppressing their stemness and inducing differentiation via down-regulation of GSK3β expression. Targeting newly identified inflammatory MC-STAT3 axis could contribute to patient tailored therapy and unveil potential future therapeutic opportunities for patients.