RESUMO
IGF-II is a polypeptide growth factor with growth and differentiation promoting activities, involved in human development. We have reported previously IGF-II mRNA and peptide overexpression in primary human colon cancers. Here we show that the IGF-II peptide content is increased in six primary colon cancers compared to the corresponding healthy tissues. The IGF-II transcripts in healthy and cancerous colon tissues were identified by Northern blotting and RT-PCR. Promoters P3 and P4 were active in most tissues. Relaxation of parental imprinting was observed in two tumors and one healthy tissue, without any correlation with the IGF-II transcript levels. Rearrangements of the IGF-II gene in two tumors containing very high amounts of IGF-II mRNA are described. Fragments containing the breakpoints were cloned by the vectorette-PCR strategy. In both tumors, the breakpoints occurred in repetitive sequences. In one tumor (T11), the breakpoint was localized 2 kb downstream the end of exon 9. The second tumor (T18) contains two modified alleles. In one rearranged allele the breakpoint is located in exon 9. The exact position of the breakpoint in the second rearranged allele has not been identified. In future experiments, the correlation between the gene rearrangements and IGF-II mRNA overexpression will be studied.
Assuntos
Adenocarcinoma/genética , Neoplasias do Colo/genética , Rearranjo Gênico , Impressão Genômica , Fator de Crescimento Insulin-Like II/genética , Adenocarcinoma/química , Neoplasias do Colo/química , Primers do DNA , DNA de Neoplasias/análise , Regulação Neoplásica da Expressão Gênica , Humanos , Fator de Crescimento Insulin-Like II/análise , Polimorfismo de Fragmento de Restrição , Regiões Promotoras Genéticas/fisiologia , RNA Mensageiro/análise , RNA Neoplásico/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Tumorais CultivadasRESUMO
The expression of members of the IGF system in a mesothelioma from a patient suffering from hypoglycemia, in term placenta and HT29 colon adenocarcinoma cells were compared. Very high levels of IGF-II mRNA and protein were detected in the mesothelioma. Moreover, half of the IGF-II protein took the high-molecular-weight form. We also analyzed the parental imprinting status and the promoter usage of the IGF-II gene. Our results showed loss of imprinting (LOI) in the mesothelioma while the imprinting was maintained in HT29 cells, expressing moderate levels of the transcript. Promoter P4 was active in the three tissues we analyzed, whereas IGF-II mRNA transcription from promoter P3 was only detected in the mesothelioma and the placenta, expressing comparably high levels of the transcript. IGF-II gene structure was identical in the analyzed tissues and cells. The type-I receptor mRNA expression was very low in the tumor. IGFBP-2, -4 and -5 mRNAs were detected in the mesothelioma, while IGFBP-2, -3 and -5 transcripts were detected in the placenta. IGFBP-1 and -6 transcripts were not detected.
Assuntos
Fator de Crescimento Insulin-Like II/genética , Mesotelioma/metabolismo , Neoplasias Pleurais/metabolismo , Somatomedinas/metabolismo , Idoso , Idoso de 80 Anos ou mais , Alelos , Northern Blotting , Feminino , Expressão Gênica/genética , Impressão Genômica , Células HT29 , Humanos , Proteína 1 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Proteína 2 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Proteína 3 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Proteína 4 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Proteína 5 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Proteína 6 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Masculino , Mesotelioma/química , Placenta/química , Placenta/metabolismo , Neoplasias Pleurais/química , Reação em Cadeia da Polimerase , Regiões Promotoras Genéticas/genética , RNA Mensageiro/análise , RNA Mensageiro/genética , RNA Ribossômico 18S/análise , RNA Ribossômico 18S/genética , Radioimunoensaio , Receptor IGF Tipo 1/análise , Receptor IGF Tipo 1/genética , Transcrição Gênica/genéticaRESUMO
The process of lymphocyte trafficking is mainly regulated by receptors that belong to a group of molecules referred to as adhesion molecules. These molecules can be divided, according to their molecular structure, into three broad families: the integrins; the selectins; and the immunoglobulin superfamily members. The alpha 4 beta 7 integrin is expressed on some lymphocytes with hallmarks of gut tropism. alpha 4 beta 7, among others, serves as a ligand for the mucosal vascular addressin MadCAM-1, which is selectively expressed on mucosal lymphoid organ high endothelial venules and on gut lamina propria venules. It is tempting to believe that related integrin receptors play a crucial role in the recirculation of activated lymphocytes between the gut mucosa and the synovial membrane.
