Alteration and enhanced expression of the c-myc oncogene in human colorectal carcinomas

We examined the alteration and expression of c-myc gene in 52 human colorectal carcinomas using Southern blot, Northern blot, Western blot and immunohistochemical techniques. Out of the 52 cases, only one case showed c-myc gene amplification of more than 4-fold. The overexpression of c-myc gene was detected in the tumor tissue of 47 cases (90.4%). In Western blot analysis, the c-myc gene related proteins were detected in the tumor tissues which had the overexpression of c-myc gene. Immunohistochemically, c-myc p62 positive tumor cells were found in 24 cases (46.2%), while the stromal cells around the tumor cells showed c-myc p62 immunoreactivity in all cases (100%). The expression of c-myc gene and c-myc P62 protein did not correlate with histological type, depth of tumor invasion and stage grouping. These findings indicate that the high incidence of the overexpression of c-myc mRNA in tumor tissues might account for the c-myc gene expression not only in tumor cells but also in stromal cells including lymphocytes, macrophages and fibroblasts.