Genetic Alterations in Colorectal Tumorgenesis

Abstract

Recent studies revealed that multiple alterations of oncogenes and tumor suppressor genes were accumulated during development of colorectal tumor. Activation of Ki-ras oncogene with point mutation is frequently detected in malignant tumors, as well as, in benign adenomas. Based on detailed studies on chromosomal deletions in tumor, two candidate tumor suppressor genes, p53 on chromosome 17p and DCC gene on chromosome 18q, were identified. These two genes are often inactivated in colorectal cancers by deletion, point mutation or insertion. Cytogenetic and linkage studies have shown that chromosomal region 5q21 harbors the gene responsible for familial adenomatous polysosis (FAP). Furthermore, this chromosomal region is often deleted in sporadic colorectal tumors. Recently, we have isolated a gene (MCC gene) located at 5q21 region that is mutated in colorectal cancers and a candidate for the putative colorectal tumor suppressor gene.