RESUMO
PURPOSE: Familial adenomatous polyposis is characterized by the development of hundreds of adenomatous polyps located mainly in the colon and rectum. Patients with familial adenomatous polyposis who do not receive treatment will develop cancer before aged 40 years. This disease is caused by germline mutations in the adenomatous polyposis coli gene. Different studies have shown a correlation between the location of the mutation and the clinical phenotype, such as the grade of severity and/or the presence of extracolonic manifestations, such as desmoid tumors. This study was designed to identify germline mutation in the adenomatous polyposis coli gene in Chilean families with familial adenomatous polyposis. METHODS: We examined the adenomatous polyposis coli gene in 24 Chilean families with familial adenomatous polyposis. The adenomatous polyposis coli gene was screened for mutations combining single strand conformation polymorphism technique, protein truncation test, and DNA sequencing. RESULTS: We detected 17 different truncating mutations in 21 of 24 families (87.5 percent); 9 of these were novel. Fourteen mutations were detected in exon 15, being the most frequent c.3,927_3,931delAAAGA, found in 3 of 21 families (14 percent). Eight families (33 percent) showed at least one patient affected with desmoid tumors, presenting mutations between codons 849 and 1,533. Interestingly, two mutations, c.3,632dupA and c.3,783_3,784delTT, leading into a truncating protein at codons 1,216 and 1,274, were associated with almost 100 percent penetrance for desmoid tumors among relatives. CONCLUSIONS: We achieved 87 percent mutation detection rate in adenomatous polyposis coli gene; more than 50 percent of them were novel. The high percentage of novel mutations found may be because of the genetic composition of the Chilean population, which is an admixture of Amerindian and Spaniards, and the scarce information in the literature about similar populations.
Assuntos
Polipose Adenomatosa do Colo/genética , DNA de Neoplasias/genética , Família , Genes APC/fisiologia , Testes Genéticos/métodos , Polipose Adenomatosa do Colo/diagnóstico , Polipose Adenomatosa do Colo/epidemiologia , Adulto , Criança , Chile/epidemiologia , Predisposição Genética para Doença , Humanos , Mutação , Polimorfismo Conformacional de Fita Simples , PrevalênciaRESUMO
BACKGROUND: Among colorectal cancer hereditary variants, two syndromes show a predisposition to the disease based on germline mutations: Familial Adenomatous Polyposis (FAP) and Hereditary Nonpolyposis Colorectal Cancer (HNPCC). AIM: To screen mutations in FAP and HNPCC families in Chile. MATERIALS AND METHODS: Two FAP and one HNPCC families were studied. The APC gene (for FAP patients) and the MLH1 gene (for HNPCC patients), were screened for mutations on genomic DNA. The molecular analysis was performed through polymerase chain reaction, Single Strand Conformer Polymorphism (SSCP) and DNA sequencing. Mutations were defined as changes in the DNA sequence leading into a stop codon and a truncated protein. RESULTS: In the two FAP families the analysis revealed a mutation consisting in the deletion of five nucleotides named c.3927_3931delAAAGA. The genetic study of the HNPCC family demonstrated the insertion of one adenine in codon 168 of exon 6, named c.504insA. DISCUSSION: Germ-line mutations were identified in the three families. The relevance of these studies in a better knowledge of cancer susceptibility, and the possibility of identifying in relatives in risk by molecular diagnosis.
Assuntos
Polipose Adenomatosa do Colo/genética , Neoplasias Colorretais/genética , Genes APC/fisiologia , Mutação/genética , Adolescente , Adulto , Neoplasias Colorretais/diagnóstico , Neoplasias Colorretais Hereditárias sem Polipose/genética , Feminino , Frequência do Gene , Mutação em Linhagem Germinativa/genética , Humanos , Masculino , Pessoa de Meia-Idade , Linhagem , Análise de Sequência de DNARESUMO
Background: Among colorectal cancer hereditary variants, two syndromes show a predisposition to the disease based on germline mutations: Familial Adenomatous Polyposis (FAP) and Hereditary Nonpolyposis Colorectal Cancer (HNPCC). Aim: To screen mutations in FAP and HNPCC families in Chile. Materials and Methods: Two FAP and one HNPCC families were studied. The APC gene (for FAP patients) and the MLH1 gene (for HNPCC patients), were screened for mutations on genomic DNA. The molecular analysis was performed through polymerase chain reaction, Single Strand Conformer Polymorphism (SSCP) and DNA sequencing. Mutations were defined as changes in the DNA sequence leading into a stop codon and a truncated protein. Results: In the two FAP families the analysis revealed a mutation consisting in the deletion of five nucleotides named c.3927_3931delAAAGA. The genetic study of the HNPCC family demonstrated the insertion of one adenine in codon 168 of exon 6, named c.504insA. Discussion: Germ-line mutations were identified in the three families. The relevance of these studies in a better knowledge of cancer susceptibility, and the possibility of identifying in relatives in risk by molecular diagnosis.
Assuntos
Adolescente , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Polipose Adenomatosa do Colo/genética , Neoplasias Colorretais/genética , Genes APC/fisiologia , Mutação/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Neoplasias Colorretais/diagnóstico , Frequência do Gene , Mutação em Linhagem Germinativa/genética , Linhagem , Análise de Sequência de DNARESUMO
O câncer colorretal ainda é uma das neoplasias de maior importância no mundo ocidental. O grande desenvolvimento da genética e biologia molecular nos últimos anos permitiu um melhor conhecimento dos mecanismos biomoleculares no câncer, e em especial, no câncer colorretal. Oncogenes (K-ras), genes supressores de tumor (p53, DCC e APC) e genes reparadores de DNA (hMSH2, MLH1, PMS1 e 2) estäo envolvidos na progressäo da seqüência adenoma-carcinoma no cólon e no reto. Algumas características anatômicas, histopatológicas, epidemiológicas e o comportamento biológico dos tumores parecem estar relacionados com alteraçöes genéticas específicas nestes genes. O conhecimento dos mecanismos genéticos que promovem a carcinogênese dos tumores colorretais abre novas perspectivas para o diagnóstico, tratamento, prognóstico e seguimento dos pacientes acometidos por esta neoplasia