Overexpression ofrasis an independent prognostic factor in colorectal adenocarcinoma

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Abstract
The expression ofraswas investigated by using immunohistochemistry in 245 primary colorectal adenocarcinomas and 49 corresponding metastases in the lymph nodes. One hundred and forty‐four (59%) of the primary tumours presented asraspositive and 37 (76%) were positive in metastases. Therasexpression was positively related to cell proliferation (p=0.01) and significantly increased in tumours with aneuploidy (68%) compared to tumours with diploidy (51%) and tetraploidy (53%, p=0.01). The frequency ofrasexpression was increased from Dukes' stage A to stages B—D (41%vs62%, p=0.01).rasexpression was compared in 40 paired primary tumours and their corresponding metastases, and the difference in expression did not reach statistical significance (73%vs83%, p=0.32). In survival analyses,rasoverexpression predicted a poor prognosis independent of Dukes' stage, DNA ploidy and S‐phase fraction (p=0.049). We did not find any significant relationship betweenrasexpression and patients' sex, age, tumour location, growth pattern, differentiation, p53 expression or heat shock protein. The results indicate that the alteration ofrasexpression may be involved in the instability of DNA and cellular overproliferation, but not in the progression to advanced stage and the development of metastases. The expression ofraswas an important biological marker for evaluating the prognosis in patients with colorectal adenocarcinoma.