Down-regulation of ribosomal protein L22 in non-small cell lung cancer

Ribosomal protein L22 (RPL22), an RNA-binding protein, is a constituent of the 60S large ribosomal subunit. As reported, RPL22 is not required in protein synthesis, and mutations of RPL22 were the main cause of macrolide resistance in bacteria. In vertebrates, RPL22 mutation might increase the proliferation of cells and then increase cancer risk. However, to our knowledge, RPL22 has not been implicated in any lung diseases, especially in lung cancer. In this study, we compared the expression of RPL22 gene in non-small cell lung cancer (NSCLC) tissues, plasma as well as human lung cancer cell line LTEP-a-2 with that in normal lung tissues and cells, using real-time RT-qPCR, Western blot, quantitative immunohistochemistry analysis, and ELISA. Our studies showed that the expression of RPL22 was significantly down-regulated in mRNA and protein expression level in NSCLC; however, there was no significant difference of RPL22 levels in plasma between normal and NSCLC patients. Further analysis indicated that down-regulation of RPL22 might be involved in the carcinogenesis of NSCLC, yet not an effective biomarker in plasma for early diagnosis.