SP1 and cancer: The CyR61 promoter, which is responsive to the transcription factor Sp1 (specificity protein 1), has been shown to be activated by various factors that are relevant for the pathogenesis of cancer, such as hypoxia-inducible factor-1α, cAMP response element binding protein (CREB) and activator protein-1 (AP-1) [[45], [46], [47]].