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The RIN1 gene, located on chromosome 11q13.2, is a molecule consisting of a coding region of 2352 bp, has a domain on the 3' side that binds to H-Ras protein, and is presumed to be an important molecule in an intracellular signaling pathway. Since the RIN1 molecule belonging to the effector molecules of H-Ras has not been reported in colorectal or other digestive tract cancers to date, we investigated how the RIN1 gene was involved in colorectal cancer. Fifty-two (51.5%) of 101 colorectal cancer specimens strongly expressed the RIN1 gene compared to the adjacent normal colorectal tissue. The 5-year survival rate of patients positive for the expression of the RIN1 gene was significantly poorer at 55% than that (83%) of patients negative for the expression of the RIN1 gene. Also, we confirmed that RIN1 protein was localized chiefly in the cytoplasm of colorectal cancer cell lines, and bound to 14-3-3 protein, but not to Ras protein.These results indicate that the RIN1 gene serves as an important signal transduction system for evaluating the malignancy of colorectal cancer. Materials and methodsCell culture. The human colorectal cancer cell lines, SW480, LoVo, DLD1, and HT29, were cultured at 37˚C in 5% CO 2 in RPMI-1640 containing 10% heat-inactivated fetal calf serum.Patients and tissue samples. The tissue specimens examined were taken from 101 colorectal cancer patients who underwent resection. Immediately after resection, necrotic and ulcerated parts of the tumors were removed and normal colorectal mucosae were dissociated from the muscle and connective tissues. All tissue specimens were then frozen in liquid nitrogen and stored at -80˚C.All patients had been treated at the First Department of Surgery, University of Fukui, between 1990 and 2000. One hundred and twenty patients consisted of 10 with stage I; 45 with stage II; 25 with stage III; and 21 with stage IV cancers

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