P53 MUTATIONS IN FLAT-TYPE AND POLYPOID-TYPE COLORECTAL TUMORS-DETECTED BY TEMPERATURE-GRADIENT GEL-ELECTROPHORESIS

Reports of cases of flat-type colorectal tumors are increasing in Japa n, but almost nothing has been elucidated about the genetic abnormalit ies of these tumors. In this study, we have examined p53 mutations in six cases of colon cancer cell lines, 22 cases of flat-type colorectal tumors, and 27 cases of polypoid-type colorectal tumors using the pol ymerase chain reaction (PCR) and temperature-gradient gel electrophore sis (TGGE); the latter has recently been developed as a screening meth od for gene mutations. p53 mutations were observed in four colon cance r cell lines, six flat-type colorectal tumors, and three polypoid-type colorectal tumors, all of which were analyzed by direct sequencing. T hese mutations were observed only in adenomas with high-grade dysplasi a and in colorectal cancers but not in adenomas with low-grade dysplas ia. These observations suggest that p53 gene mutations are involved in flat-type as well as polypoid-type colorectal tumors at relatively la ter stages of carcinogenesis and that TGGE seems to be useful as one o f the rapid screening methods.