RESUMO
Identification of genes associated with hereditary cancers facilitates management of patients with family histories of cancer. We performed exome sequencing of DNA from 3 individuals from a family with colorectal cancer who met the Amsterdam criteria for risk of hereditary nonpolyposis colorectal cancer. These individuals had mismatch repair-proficient tumors and each carried nonsense variant in the FANCD2/FANCI-associated nuclease 1 gene (FAN1), which encodes a nuclease involved in DNA inter-strand cross-link repair. We sequenced FAN1 in 176 additional families with histories of colorectal cancer and performed in vitro functional analyses of the mutant forms of FAN1 identified. We detected FAN1 mutations in approximately 3% of families who met the Amsterdam criteria and had mismatch repair-proficient cancers with no previously associated mutations. These findings link colorectal cancer predisposition to the Fanconi anemia DNA repair pathway, supporting the connection between genome integrity and cancer risk.
Assuntos
Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo do DNA/genética , Exodesoxirribonucleases/genética , Mutação em Linhagem Germinativa , Adulto , Idoso , Idoso de 80 Anos ou mais , Linhagem Celular Tumoral , Pré-Escolar , Neoplasias Colorretais Hereditárias sem Polipose/enzimologia , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Endodesoxirribonucleases , Exodesoxirribonucleases/metabolismo , Feminino , Predisposição Genética para Doença , Células HEK293 , Hereditariedade , Humanos , Masculino , Pessoa de Meia-Idade , Enzimas Multifuncionais , Linhagem , Fenótipo , Adulto JovemRESUMO
Fanconi anemia (FA) is a rare bone marrow failure disorder with defective DNA interstrand crosslink repair. Still, there are FA patients without mutations in any of the 15 genes individually underlying the disease. A candidate protein for those patients, FA nuclease 1 (FAN1), whose gene is located at chromosome 15q13.3, is recruited to stalled replication forks by binding to monoubiquitinated FANCD2 and is required for interstrand crosslink repair, suggesting that mutation of FAN1 may cause FA. Here we studied clinical, cellular, and genetic features in 4 patients carrying a homozygous 15q13.3 micro-deletion, including FAN1 and 6 additional genes. Biallelic deletion of the entire FAN1 gene was confirmed by failure of 3'- and 5'-PCR amplification. Western blot analysis failed to show FAN1 protein in the patients' cell lines. Chromosome fragility was normal in all 4 FAN1-deficient patients, although their cells showed mild sensitivity to mitomycin C in terms of cell survival and G(2) phase arrest, dissimilar in degree to FA cells. Clinically, there were no symptoms pointing the way to FA. Our results suggest that FAN1 has a minor role in interstrand crosslink repair compared with true FA genes and exclude FAN1 as a novel FA gene.