All-trans retinoic acid enhances cytotoxicity of CIK cells against human lung adenocarcinoma by upregulating MICA and IL-2 secretion

To determine the growth inhibition capability of all-trans retinoic acid (ATRA) with cytokine-induced killer cells (CIKs), we evaluated their effects, alone and in combination, on human lung carcinoma A549 cells. CIKs treated with ATRA significantly inhibited cell growth. Additionally, CIK with ATRA synergistically inhibited migration and invasiveness, colony formation of A549 and NCI-H520 cells. Furthermore, analysis of apoptosis markers Bcl-2, Bax, Survivin and cleaved Caspase-3 showed that Bcl-2 and Survivin mRNA levels significantly decreased, and that Bax mRNA significantly increased, in the CIK + ATRA-treated cells, with corresponding effects on their respective proteins. The involved mechanisms may be associated with upregulated expression of MHC class I-Related Chain (MICA) and interleukin (IL)-2. These results suggest that administration of combined CIK and ATRA is a potentially novel treatment for lung carcinoma.