Specifically, changes that increase GBM cells' secretion of cytokines, such as transforming growth factor-β (TGF-β) and interleukin-10 (IL-10), promote immunosuppressive cell recruitment and cancer progression.17 By suppressing the activity of immune cells, GBM cells can proliferate without checks on their growth. This evidence concerns the gene TGFB1 and glioblastoma.