Raf kinase inhibitor protein (RKIP) expression in stage II colorectal cancer and its clinical significance

Objective: To explore the relationship of Raf kinase inhibitor protein(RKIP)expression in tumor tissue and corresponding adjacent normal tissue with the prognosis of stage Ⅱ colorectal cancer (CRC) patients. Methods: The clinical data and tumor tissue specimens of 130 stage Ⅱ CRC patients after radical operation were collected. The expression of RKIP was detected by immunohistochemistry using SP method. In addition to the clinical characteristics of the patients, the relationship between RKIP expression and the prognosis of the patients was explored. Results: RKIP expression in primary tumor tissue was down-regulated compared with that in adjacent normal tissue (P<0.001). RKIP expression levels in primary tumor tissue from metastatic patients were lower than those from non-metastatic patients (P=0.034). The RKIP strong expression group had significantly longer disease free survival (DFS) than the RKIP low/medium expression group (10 yr DFS, 89% vs. 75%, P=0.032). Overall survival (OS) of the RKIP strong expression group was longer than the RKIP low/medium expression group with no significant difference (10 yr OS, 88% vs. 71%, P=0.058). Low RKIP expression (HR 0.37; 95% CI, 0.13-0.99; P=0.040)and increased preoperative serum CEA level (HR 0.37; 95% CI, 0.13-0.99; P=0.013) were the risk factors of relapse/metastasis for stage Ⅱ CRC patients. Conclusion: RKIP expression was down-regulated in primary tumor tissue. The patients with strong RKIP expression had longer disease free survival. It is suggested that RKIP expression may be correlated with the relapse/metastasis of stage Ⅱ CRC patients after radical operation, although further research is required to confirm this.