RCAS1 expression: a potential prognostic marker for adenocarcinomas of the lung.

RCAS1 (receptor-binding cancer antigen expressed on SiSo cells) is a new tumor-associated antigen recognized by 22-1-1 monoclonal antibody. RCAS1 expressed on human cancer cells acts as a ligand for a putative receptor present on peripheral lymphocytes. RCAS1 has been shown to inhibit the in vitro growth of receptor-expressing cells and to induce apoptosis, which may contribute to the ability of tumor cells to evade host immune surveillance. In this study, we evaluated the prognostic significance of RCAS1 expression in primary lung adenocarcinomas. Immunohistochemical analysis was performed on tissue specimens surgically obtained from 102 patients with primary lung adenocarcinomas. Then, the association of RCAS1 expression with clinicopathological variables and prognosis of patients were analyzed. Of 102 lung adenocarcinomas, positive RCAS1 expression was observed in 82 cases (80%). There was no correlation between RCAS1 expression and clinicopathological variables. In 70 potentially curatively resected lung adenocarcinomas, patients with RCAS1-positive tumors had a significantly shorter survival than those with RCAS1-negative tumors (p = 0.02), and RCAS1 expression was a significant and independent prognostic factor by multivariate analysis (p = 0.03). These results indicate that RCAS1 expression predicts prognosis in patients with lung adenocarcinomas, and this new antigen could be a novel tumor marker which reflects the clinical outcome of lung cancers.