Since TSP-1 inhibits angiogenesis and GFAP is associated with a more differentiated astrocytic phenotype [45], these results suggested that, in addition to promoting glioma cell mitogenesis, expression of IE1 in glioma cells may also promote GBM angiogenesis, and a de-differentiated state, along with loss of tumor suppressor activity. This evidence concerns the gene THBS1 and glioma.