K-ras Gene Mutations and Expression of K-ras, p16, Cyclin D1 and p53 in Synchronous Lesions of The Colon Adenoma-Carcinoma Sequences

ABSTRACT

BACKGROUND: The colorectal adenoma-carcinoma sequence represents a well-known para-digm for the sequential development of cancer driven by the accumulation of genomic defects. Although the colorectal adenoma-carcinoma sequence has been well investigated, the studies about tumors of different dignity co-existent in the same patient are rare. K-ras mutation is an early genetic change in colon cancer. The genes involved in the cell cycle such as cyclin D1, p16, and p53 are important in the tumorigenesis of the colon. The aims of this study were to determine K-ras gene mutation and expression of K-ras, p16, cyclin D1 and p53 in synchronous lesions of the colon adenoma-carcinoma sequences and their possible relationship with K-ras mutation. METHODS: The materials included 45 colonic adenocarcinomas which were accompanied by adenoma (22 low grade and 26 high grade). By using polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP), we detected K-ras mutation of codon 12. An aberrant K-ras, p16, cyclin D1 and p53 expressions were stained using an immunohistochemical method. RESULTS: K-ras mutation was 52.4% (11/21) of high grade adenomas. K-ras expression was 65.4% (17/26) of high grade adenomas. p16 and cyclin D1 expressions were 50% (11/22) and 90.9% (20/22) of low grade adenomas, respectively. p53 expression was 75.6% (34/45) of adenocarcinomas. There were statistical correlations among K-ras, p16 and cyclin D1. CONCLUSIONS: These results indicate that the ras gene mutation is an early event and the overexpressions of p16, cyclin D1 and p53 are associated with K-ras mutation and expression in adenoma-carcinoma sequences.