Expression of tumor-associated antigen RCAS1 correlates significantly with poor prognosis in nonsmall cell lung carcinoma

BACKGROUND. RCAS1 is a recently discovered antigen molecule expressed on the membrane of cancer cells, and it acts as a ligand for a putative receptor present on immune cells such as T, B and NK cells. It has been suggested that RCAS1 expression is related to the escape of tumors from immune surveillance. In this study, the relation between RCAS1 expression and various clinicopathologic variables, including patient prognosis, was investigated in lung carcinoma through immunohistochemical analysis. METHODS, One hundred two surgically resected nonsmall cell lung carcinoma cases were examined histopathologically by means of the monoclonal antibody 22-1-1, which is specific for RCAS1. The correlation between RCAS1 expression and the clinicopathologic features of patients was evaluated. Moreover, the correlation between RCAS1 expression and the survival of patients was analyzed by the Kaplan-Meier method log-rank test, and multivariate analysis was performed by using the Cox proportional hazard model. RESULTS. The samples of 48 of the 102 lung carcinoma patients (47.1%) were positive for RCAS1. There were significant correlations between RCAS1 expression and either pathologic staging (P = 0.0003) or tumor differentiation (P = 0.0308). The survival time for the RCAS1-positive group was significantly shorter than that for RCAS1-negative group (P < 0.0001). Moreover, multivariate analysis for overall survival revealed that RCAS1 expression was a significantly independent prognostic factor in nonsmall cell lung carcinoma patients. CONCLUSION. These results suggested that RCAS1 expression may play an important role in the immune escape mechanism and that RCAS1 expression may be a good indicator of poor prognosis in patients with nonsmall cell lung carcinoma.