GLI1 and neoplasm: Although the fusion protein has multiple functions, one of its primary roles is as a transcription factor, increasing the expression of many downstream targets involved in tumor survival and growth [for example, IGF1 (6), GLI1 (7), Myc (8), ID2 (9)], while decreasing expression of cell cycle regulators and pro-apoptotic genes [for example, TGFB2 (10), p21 (11), IGFBP3 (12)].