MDM2 and cancer: One regulatory SNP is thought to act as a low-penetrance cancer susceptibility factor in its own right: homozygosity for the intronic 309T>G MDM2 variant (rs2279744), which leads to enhanced binding of the Sp1 transcription factor and MDM2 up-regulation, appears to increase the risk for many types of tumour, presumably in concert with other lesions (Hu et al. 2007).