STAT3 and glioblastoma: In this regard, it was reported that glioblastoma stem cell-derived exosomes skew monocytes toward an immunosuppressive M2 phenotype, through the STAT3 pathway, fostering PD-L1 expression and cytokines production, such as MCP-3 and CXCl1, which further enhance the recruitment of myeloid cells into TME.