A functional variant in miR-605 modifies the age of onset in Li-Fraumeni syndrome

Li-Fraumeni syndrome (LFS) is a rare cancer predisposition syndrome, typically associated with germline mutations in the TP53 gene. Despite the high penetrance of TP53 mutations, LFS patients display striking phenotypic differences, suggesting the presence of secondary risk loci. To date, all genetic modifiers in LFS have been shown to map to either TP53 or its principal negative regulator, MDM2. Given this strong association, we set out to investigate the contribution of miR-605, a recently described microRNA (miRNA) regulator of the p53-MDM2 loop. We hypothesized that, if functional, the miR-605 gene and its variant (rs2043556) could impact the cancer risk profile of TP53 mutation carriers. Consistent with this proposition, the variant G-allele of miR-605 was associated with a 10-year acceleration in the mean age of LFS tumor onset (P = 0.04) and caused a 2.6-fold reduction in the processing levels of its host miRNA (P < 0.05). We also demonstrate that miR-605 overexpression leads to a decrease in cell proliferation, clonogenicity, and migration in two rhabdomyosaroma cell lines carrying hotspot TP53 mutations. Together, our results implicate miR-605 as a novel modifier gene of the LFS phenotype and a promising therapeutic target in TP53 mutant cancers.