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.

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