Oncogene expression in colorectal carcinomas

The expression of oncogenes plays a central role in the regulation of cell growth in normal and neoplastic tissue. Techniques developed recently (blot and in situ hybridization), enable the quantitative detection and topographical localization of oncogene expression at DNA and RNA level. In colonic adenomas and carcinomas and in non neoplastic mucosa of the large bowel, expression products of the oncogenes Ha-ras, Ki-ras, fos, and c-myc were detected. In most tumors a significant overexpression - as compared to the normal mucosa - of Ha-ras, Ki-ras, and fos mRNA was found. The overexpression of oncogenes, however, did not correlate with tumor progression, neither qualitatively nor quantitatively. According to recent studies it can be concluded, that the expression of the Ki-ras gene altered by a single point mutation, contributes significantly to the initiation and progression of epithelial neoplasias of the colon mucosa. It can be concluded, therefore, that the demonstration of oncogene expression products will play an important role in tumor diagnosis in the future.