After stratifying according to MDM2 SNP309 status, we found a reduced risk for breast cancer among individuals harboring the MDM4 SNP34091CC/MDM2 SNP309GG genotype, and this association was stronger after removing individuals harboring the MDM2 SNP285C allele, previously shown to antagonize SNP309G‐induced transcription elevation 16. Here, MDM2 is linked to breast cancer.