SP1 and glioblastoma: US28 is widely expressed in human glioblastoma and displays oncomodulatory activity by activating a broad panel of transcription factors, such as NF-kB, nuclear factor of activated T cell (NFAT), CREB, STAT3, activator protein-2 (AP-2), stimulating protein 1 (Sp1), TCF/LEF, and hypoxia inducible factor-1 (HIF-1)7, 8, 10, 73, 74, 75, 76.