RESUMO
Interleukin-10-deficient mice develop colitis and colorectal cancer similar to the inflammatory bowel disease associated cancer in humans. The aim of this study was to identify possible mutations of oncogenes and tumour suppressor genes involved in tumorigenesis in Interleukin-10 (IL-10)-deficient mice. Twenty colon carcinomas from IL-10-deficient mice were screened for mutations in the K-ras and p53 genes by 'cold' single-strand-conformation polymorphism. Immunohistochemical staining was performed to detect mutations in the proteins P53, APC and MSH2, and the transforming growth factor beta type II receptor. Microsatellite instability was analysed at eight chromosomal loci and plasma levels of transforming growth factor beta1 (TGF-beta1) were also measured. At 9 weeks, 14% of the animals developed colorectal cancer, and at 10-31 weeks the incidence of carcinoma was 65%. No mutations were detected in the analysed oncogene and tumour suppressor genes. Plasma TGF-beta1 levels in IL-10-deficient mice 10-31 weeks old were higher than in wild-type littermates e.g. 45.7 +/- 4.6 ng/ml versus 19.8 +/- 4.5 ng/ml (P<0.01). No alterations in K-ras, p53, APC: and Msh2 genes suggests that other genes are involved in the development of these tumours. Elevated TGF-beta1 plasma levels correspond to the high incidence of dysplasia and cancer. Normal expression of the TGF-beta II receptors hints at genetic alterations in other members of the TGF-beta receptor signal transduction pathway.
Assuntos
Proteínas de Ligação a DNA , Doenças Inflamatórias Intestinais/genética , Interleucina-10/genética , Mutação , Neoplasias/genética , Proteína da Polipose Adenomatosa do Colo , Animais , Carcinoma/genética , Neoplasias do Colo/genética , Neoplasias Colorretais/genética , Proteínas do Citoesqueleto/genética , Genes p53/genética , Genes ras/genética , Humanos , Imuno-Histoquímica , Intestino Grosso/patologia , Intestino Delgado/patologia , Camundongos , Camundongos Endogâmicos C57BL , Repetições de Microssatélites , Proteína 2 Homóloga a MutS , Polimorfismo Conformacional de Fita Simples , Proteínas Serina-Treonina Quinases , Proteínas Proto-Oncogênicas/biossíntese , Proteínas Proto-Oncogênicas/genética , Receptor do Fator de Crescimento Transformador beta Tipo II , Receptores de Fatores de Crescimento Transformadores beta/biossíntese , Análise de Sequência de DNA , Transdução de Sinais , Fator de Crescimento Transformador beta/sangue , Fator de Crescimento Transformador beta1RESUMO
We examined 36 cases of human sporadic colon carcinoma and corresponding normal tissue samples to evaluate loss of heterozygosity at the APC and DCC tumor suppressor genes loci using restriction fragment length polymorphism polymerase chain reaction and variable nucleotide tandem repeat analysis. Observed informativity was 83% for APC and 75% for DCC. DNA from 6 (20%) of 30 informative tumors exhibited loss of heterozygosity at the APC locus. Loss of heterozygosity at the DCC locus was observed in 7 (26%) of 27 informative tumor DNAs. Our results support the view that malignant progression is a consequence of more than one genetic change and suggest that inactivation of APC and DCC genes plays a role in a multistep process of colon tumor progression.