Heterotypic cell-cell interactions between malignant cells with high integrin β8 expression and those with low integrin β8 expression result in high TGFβ signaling in the integrin β8–low cells, which is associated with markers of glioblastoma differentiation, and low TGFβ signaling in the integrin β8–high tumor cells, which is associated with the expression of CSC markers, DNA repair, and mitosis. The gene discussed is TGFB1; the disease is glioblastoma.