Clinical significance of altered expression of the retinoid acid receptors alfa and beta (RAR a and b) and the cellular retinol binding protein (CRBP-1) in stage I non-small cell lung cancer

Abstract

18117 Background: Retinoids, a group of natural and synthetic Vitamin A analogues, are known to play a major role in regulating growth, differentiation and apoptosis of many cell types. Its role as prognostic factors in non-small cell lung cancer (NSCLC) is poorly known. Methods: Patients who underwent a successful surgical resection for stage I NSCLC were elegible. Antigen expression was analyzed by immuno histochemistry on histological samples of the tumor to investigate the expression pattern of RARa, RARb and CRBP-1. 51 NSCLC patients stage I (18 Stage Ia and 33 Stage Ib) were tested . A case was considered positive when more than 10% of cells presented specific staining for the antigen. Prognostic evaluation was performed with the Log-Rank test and the multivariate proportional hazard model. Results: About 40% of cases were positive for RARa. In the case of RARb 58.3% NSCLC showed cytoplasm staining, while only 18% showed nuclear immunopositivity. Taken together, the 81.5% of NSCLC tumors expressed at least one RA receptor (RARa or RARb or both). CRBP-1 staining was observed in 52% of the lung tumors. No relationship was found between the number of cells expressing the studied molecules and clinical pathological features, including sex, T stage, histopathology, adjuvant therapy, smoking habit or the presence of tumor cells in the pleural fluid. The only exception was that a higher percentage of adenocarcinomas were positive for RARa as compared with epidermoid tumors (50.0 vs 14.3%, p=0.05). On the other hand RARb was expressed preferentially in epidermoid tumors (81.3% vs 42.9 %, p<0.05). Univariate analysis showed a significant association between positive expression of RARb with shorter overall survival (log-rank test 3.7, p<0.05). However, the multivariate study indicated that RARb expression was influenced by other clinical pathological parameters, suggesting that this antigen would not be able to predict cancer-specific survival in an independent way. Conclusions: A high number of stage I NSCLC express RARs and CRBP. This suggests that retinoid expression could harbour relevant prognostic information at an early stage of the disease. No significant financial relationships to disclose.