SP1 and melanoma: Considering the increased affinity of Sp1 for its binding site in position 309 of the MDM2 promoter when G is present and that the G-allele has been linked to increased MDM2 mRNA and Mdm2 protein [14,15], and that higher levels of MDM2 predict better outcomes in melanoma [39], our findings of a protective effect in carriers of MDM2 SNP309*G are biologically plausible.