Increased level of mitochondrial gene expression in polyps of familial polyposis coli patients.

To elucidate the mechanism of polyp formation in familial polyposis coli patients, cDNA clones, expressed differently between normal colonic mucosae and polyps, were screened. Three polyp-derived cDNA clones showed increased levels of transcription under neoplastic conditions. Among them, clone P6 was determined to be derived from the mtDNA encoding parts of subunit 1 of NADH dehydrogenase and 16S rRNA. The number of copies and restriction enzyme patterns of the mtDNA did not vary in either normal or neoplastic tissues, and a level of different mitochondrial mRNA was increased in the same proportion, suggesting a change in the rate of synthesis and/or degradation of the mtRNA. No cDNA clone which was expressed higher in normal colonic mucosae than in polyps was isolated from the cDNA library derived from normal mucosae.