GLI1 and breast cancer: Furthermore, tGLI1 is a gain-of-function transcription factor that, in addition to regulating known GLI1 target genes, is able to modulate expression of genes not regulated by GLI1 to induce several oncogenic phenotypes in breast cancer and glioblastoma such as tumor growth, migration and invasion, angiogenesis, maintenance of the cancer stem cell (CSC) population, metastasis, and astrocyte activation [24,25,28,29,30,31,32,33].