Molecular analysis of Fanconi anemia and mismatch repair genes in patients with colorectal carcinoma

A cohort of 206 consecutively-collected patients with colorectal carcinoma (CRC) were screened for germline mutations in the principal DNA mismatch repair (MMR) genes, MLH1 and MSH2, and in the Fanconi anemia (FA) genes involved in homologous recombination DNA repair. Mutation analysis was performed by denaturing high-performance liquid chromatography (DHPLC) and automated sequencing. Available paraffin-embedded tumor tissues were evaluated for gene expression by immunohistochemistry. Genes of the FA pathway were found to participate in CRC pathogenesis, being silenced during disease progression and metastasis formation. Conversely, MLH1 and MSH2 genes seem to be inactivated at earlier stages of the disease. Finally, very few (about 5%) cases presented a simultaneous inactivation of the MMR and FA genes. Overall, our findings indicated that: i) mismatch DNA repair remains the main mechanism to be altered at both germline and somatic levels among CRC patients; ii) functional impairments of mismatch DNA repair and FA-related repair may represent two different pathogenetic alterations which are concurring in colorectal cancer progression.