Proteomic analysis of the small intestine and colon epithelia of adenomatous polyposis coli gene-mutant mice by two-dimensional gel electrophoresis

Mutations of the adenomatous polyposis coli gene (APC) have been implicated in the occurrence of sporadic colon cancer. Various APC mutant strains of mice have been created to better understand the function of this gene. Prev iously, we had mice express a mutant form of mRNA of the APC protein that e ncoded 474 amino acids instead of the 2845 amino acids due to exon duplicat ion. These APC mutant mice (APC Delta 474) developed intestinal and mammary tumors, as have other APC mutant mice previously reported (Sasai, H., et a l. Carcinogenesis, in press). To elucidate the mechanism of the tumor devel opment, we prepared protein samples from both normal and tumor tissues from APC Delta 474 mutant mice, as well as tissues from normal mice, and used t hem for proteomic analysis. After two-dimensional electrophoresis, the gels were silver stained and the protein spots were analyzed. We analyzed about 1000 protein spots per sample and found several protein spots that are spe cific for normal or tumor samples from APC Delta 474 mutant mice, as well a s proteins with altered expression levels. Among the identified protein spo ts, truncated beta-tubulins were specific to APC Delta 474 mutant mice poly p samples. The apparent molecular mass of these proteins suggested that the se beta-tubulins may be truncated very close to the binding site of the ant i-tumor drug taxol.