Clinicopathological significance of ribosomal protein S6 kinase A6 in lung squamous cell carcinoma: an immunohistochemical and RNA-seq study.

Ribosomal protein S6 kinase A6 (RPS6KA6) is a downstream factor of the ERK-MAPK pathway and has been extensively studied in various types of cancer. However, the role of RPS6KA6 in lung squamous cell carcinoma (LUSC) remains unclear. This study investigated expression of the RPS6KA6 and its clinicopathological correlation with LUSC and explored genetic alterations in the ribosomal protein S6 kinase (RSK) family in LUSC and their impact on the survival of patients. Expression of the RPS6KA6 protein in 175 LUSC samples and 30 normal lung tissues samples was determined by immunohistochemistry (IHC). RPS6KA6 protein expression in the LUSC tissues was significantly higher compared with that in the normal lung tissues (P=0.017). Overexpression of RPS6KA6 protein correlated with tumor size (r=0.260, P=0.001), lymph node metastasis (r=0.683, P<0.001), and TNM stage (r=0.378, P<0.001). RPS6KA6 RNA-seq data were obtained from the Cancer Genome Atlas (TCGA) and ONCOMINE database. RPS6KA6 mRNA expression in the LUSC tissues was significantly higher than that in paired noncancerous samples (TCGA: P=0.005; ONCOMINE: P=0.018). According to the cBioPortal online software, three detecting methods, including Seqv2, Array and U133, identified that the frequency of the genetic alterations in the RSKs in LUSC were 77%, 44%, and 42%, respectively. However, survival analysis of LUSC patients with or without RSKs genetic alterations reached no statistical significance. This study suggests that RPS6KA6 may be an oncogene in LUSC, and that expression of the RPS6KA6 protein is associated with the progression of LUSC. The RSK genes are frequently altered in LUSC, but the alterations have no significant effect on the survival of patients.