CD5 and CD6 as immunoregulatory biomarkers in non-small cell lung cancer

Abstract

Background: The study of immune surveillance in the tumour microenvironment is leading to the development of new biomarkers and therapies. The present research focuses on the expression of CD5 and CD6 - two lymphocyte surface markers involved in the fine tuning of TCR signaling - as potential prognostic biomarkers in resectable stages of non-small cell lung cancer (NSCLC). Methods: CD5 and CD6 gene expression was analysed by reverse transcription quantitative polymerase chain reaction (RTqPCR) in 186 paired fresh frozen tumour and normal tissue samples of resected NSCLC. Results: Patients with higher CD5 expression had significantly increased overall survival (OS, 49.63 vs. 99.90 months, p=0.013). CD5 expression levels were correlated to CD4 infiltration and expression levels, and survival analysis showed that patients with a higher CD5/CD4+ ratio had significantly improved prognosis. Multivariate analysis established CD5 expression as an independent prognostic biomarker for OS in early stages of NSCLC [HR=0.554; 95% CI, 0.360-0.853; p=0.007]. Further survival analysis of NSCLC cases (n=97) from The Cancer Genome Atlas (TCGA) database, confirmed the prognostic value of both CD5 and CD6 expression¸ although CD6 expression alone did not reach significant prognostic value in our NSCLC training cohort. Conclusions: Our data support further studies on CD5 and CD6 as novel prognostic markers in resectable NSCLC and other cancer types (i.e., melanoma), as well as a role for these receptors in immune surveillance.