SP1 and colorectal carcinoma: It is worth mentioning that the promoter activity of integrin α5 can be modulated by several other TFs in CRC, such as parathyroid hormone-related protein (PTHrP) (Anderson et al., 2007), zinc finger E-box binding homeobox 2 (ZEB2)-SP1 (Nam et al., 2014), Twist 1 and AP-1 (Nam et al., 2015); while in GC, it has been reported that integrin α5β1 is stimulated by the loss of hypoxia-inducible factor 1a (HIF-1a), an oxygen-dependent transcriptional activator, which results in enhanced metastasis (Rohwer et al., 2008).