Alterações genômicas em pacientes e seus familiares com a síndrome do câncer colorretal hereditário / Genomic alterations in patients and their relatives with unexplained familial or early-onset colorectal cancer

RESUMO

O câncer colorretal (CCR) é a terceira neoplasia mais comum no mundo. Estima-se que 35% dos CCRs são hereditários, no entanto, apenas 5% destes casos são explicados por mutações patogênicas em genes de alta penetrância, A Síndrome de Lynch (SL) é a doença hereditária mais comum associada com o risco de CCR estando associada com mutações germinativas nos genes de reparo a erros de pareamento (Mismatch repair genes - MMR). Neste estudo foram avaliadas as alterações genômicas em 54 pacientes com a SL (critérios clínicos de Amsterdam ou Bethesda) e negativos para mutações patogênicas nos genes MMR (MLH1, MSH2, MSH6 e PMS2), TP53 ou CHEK2 (100delC); com o objetivo de identificar novos genes que poderiam estar associados com a predisposição ao CCR. As variações no número de cópias (Copy number variations - CNVs) foram avaliadas em todos os casos utilizando a plataforma de microarranjos (microarray) Agilent 4X180K, enquanto 26 casos também foram reanalisados com a plataforma Affymetrix CytoScan HD. Em 21 casos foram identificadas apenas CNVs comuns, enquanto 33 pacientes apresentaram 58 CNVs raras. Destas, 43 CNVs raras cobriram genes e foram detectadas em 28 pacientes. Nos casos avaliados com as ambas as plataformas foi possível validar 9 CNVs raras. A análise in silico revelou que 52 dos 81 genes afetados por CNVs raras foram associados com câncer, dos quais 26 estavam relacionados com o CCR...

ABSTRACT

Colorectal Cancer (CRC) is the third most common cancer worldwide. It is estimatedthat 35% of CRCs are hereditary. However, only 5% of these cases are explained bypathogenic mutations in high-penetrance genes. Lynch Syndrome (LS) is the mostcommon hereditary disease related to CRC risk being associated with germlinemutations in the mismatch repair genes (MMR). In this study, we evaluated genomicalterations in 54 LS patients (Amsterdam or Bethesda clinical criteria) negative forpathogenic mutations in MMR genes (MLH1, MSH2, MSH6 and PMS2), TP53 orCHEK2 (100delC), aiming to identify new genes that might be associated with CRCpredisposition. Copy number variations (CNVs) were assessed in all cases usingAgilent 4x180K microarray platform, while 26 cases were also reanalyzed byAffymetrix CytoScan HD platform. Twenty-one cases presented only commonCNVs, while 33 patients presented 58 rare CNVs. From these, 43 rare CNVs coveredgenes and were detected in 28 patients. Nine rare CNVs were validated in patientsevaluated by both platforms. In silico analysis revealed that 52 of the 81 genesaffected by rare CNVs have been associated with cancer, of these 26 were related toCRC. Among these alterations, an intronic deletion in ROBO1 gene was detected in ayoung patient with CRC with no family history of cancer. Coincidentally, identicaldeletion was found in two unrelated patients with family history of breast cancer,thus providing further evidence of the pathogenic effect of this CNV...