MDM2 plays a key role in modulating p53 function. The MDM2 SNP309T > G promoter polymorphism enhances Sp1 binding and has been linked to cancer risk and young age at diagnosis although with conflicting evidence. We report a second MDM2 promoter polymorphism, SNP285G > C, residing on the SNP309G allele. SNP285C occurs in Caucasians only, where 7.7% (95% CI 7.6%-7.8%) of healthy individuals carry the SNP285C/309G haplotype. In vitro analyses reveals that SNP309G enhances but SNP285C strongly reduces Sp1 promoter binding. Comparing MDM2 promoter status among different cohorts of ovarian (n = 1993) and breast (n = 1973) cancer patients versus healthy controls (n = 3646), SNP285C reduced the risk of both ovarian (OR 0.74; CI 0.58-0.94) and breast cancer (OR 0.79; CI 0.62-1.00) among SNP309G carriers.,
Cancer Cell
Erasmus MC: University Medical Center Rotterdam

Knappskog, S., Bjørnslett, M., Myklebust, L., Huijts, P., Vreeswijk, M., Edvardsen, H., … Lønning, P. (2011). The MDM2 Promoter SNP285C/309G Haplotype Diminishes Sp1 Transcription Factor Binding and Reduces Risk for Breast and Ovarian Cancer in Caucasians. Cancer Cell, 19(2), 273–282. doi:10.1016/j.ccr.2010.12.019