The value of RCAS1 as a potential biomarker in non-small cell lung cancers.

Abstract

e21098 Background: RCAS1 (Receptor-binding Cancer Antigen expressed on SiSo cells) is a membrane protein that is expressed in different types of cancer. It halts the cell cycle and/or induces the apoptosis of the immune system cells within the tumour microenvironment. Hence, it is possible that this molecule is involved in the mechanism of the tumour cells’ escape from the immune system surveillance (immunoescape). Methods: Patients with primary non small cell lung cancer, initially eligible for surgical treatment, were included. The tissue samples (paraffin cubes) were processed using the Tissue Micro-arrays Method. Immunohistochemical study was done with specific monoclonal antibodies for RCAS1 and Ki-67. The image analysis was feasible due to a special program (image analysis software). In addition, a database was created that included the clinical and pathological characteristics of the patients. After the surgery patients received chemotherapy and/or radiotherapy according to the guidelines. Associations between variables were analyzed with non-parametric tests (Mann-Whitney and Kruskal-Wallis test) and the survival analysis with the Cox proportional hazards model. Two tailed p values ≤ 0.05 were considered to be statistically significant. Results: In total, 112 patients were examined (93 men and 19 women), mean age 63,6 years old. Almost 53% of the cases were adenocarcinoma, 33% squamous cell, 9% large cell, and 5% other types. Statistical significance was identified correlating RCAS1 over-expression to lower overall survival (p=0.032), to grade III (p=0.006) and in a positive correlation between RCAS1 and Ki-67 (p<0.001). Moreover, there is a trend of RCAS1 over-expression in advanced or metastatic stages and in tumours with lymphovascular invasion. In contrast, protein expression was not strongly associated to tumour size, to histological type, to patient age or to gender. Conclusions: The most important conclusions of this study are the negative correlation between RCAS1 and overall survival, the over-expression of RCAS1 in grade III tumors and the positive correlation between RCAS1 and Ki-67 which means that when Ki-67 increases RCAS1 is higher. Consequently, this molecule RCAS1 probably could be considered as a marker of the tumor’s aggressiveness.