Role of high expression levels of STK39 in the growth, migration and invasion of non-small cell type lung cancer cells

Non-small cell type lung cancer (NSCLC) is the most common malignancy and the leading cause of cancer related mortality. In this study, serine/threonine kinase 39 (STK39) was identified as an up-regulated gene in NSCLC tissues by next-generation RNA sequencing. Although STK39 gene polymorphisms may be prognostic of overall survival in patients with early stage NSCLC, the roles of STK39 in NSCLC cancer are poorly understood. In the current study, Genome Set Enrichment Analysis (GSEA) on the RNA-seq data of NSCLC specimens indicated that cancer-related process and pathways, including metastasis, cell cycle, apoptosis and p38 pathway, were significantly correlated with STK39 expression. STK39 expression was significantly increased in NSCLC cases and its protein expression was positively correlated with the poor tumor stage, large tumor size, advanced lymphnode metastasis and poor prognosis. Down-regulation of STK39 in NSCLC cells significantly decreased cell proliferation by blocking of cell cycle and inducing apoptosis. We also found that STK39 knockdown in NSCLC cells remarkably repressed cell migration and invasion. On the contrary, overexpression of STK39 in NSCLC cells had inverse effects on cell behaviors. Taken together, STK39 acts as a tumor oncogene in NSCLC and can be a potential biomarker of carcinogenesis.