Serum- and glucocorticoid-inducible kinase 3 is a potential oncogene in nasopharyngeal carcinoma

Introduction: Serum- and glucocorticoid-inducible kinase 3, a serine/threonine kinase that functions downstream of the PI3K signaling pathway, plays a critical role in neoplastic processes. It is expressed by various tumors and contributes to carcinogenesis. Objective: The objective was to investigate serum- and glucocorticoid-inducible kinase 3 expression in nasopharyngeal carcinoma, to study the anti-tumor effects of serum- and glucocorticoid-inducible kinase 3 shRNA by inhibiting its expression in nasopharyngeal carcinoma cells and to discuss the potential implications of our findings. Methods: Serum- and glucocorticoid-inducible kinase 3 protein expression in nasopharyngeal carcinoma cell lines (CNE-1, CNE-2, HNE-1, HONE-1, and SUNE-1) and the human immortalized nasopharyngeal epithelium cell line NP69 were assayed by western blotting. Serum- and glucocorticoid-inducible kinase 3 expression in 42 paraffin-embedded nasopharyngeal carcinoma tissues were performed by immunohistochemistry. MTT assay, flow cytometry, and scratch tests were performed after CNE-2 cells were transfected with the best serum- and glucocorticoid-inducible kinase 3 shRNA plasmid selected by western blotting using lipofectamine to study its effect on cell proliferation, apoptosis, and migration. Results: Serum- and glucocorticoid-inducible kinase 3 was overexpressed in human nasopharyngeal carcinoma tissues and cells. Serum- and glucocorticoid-inducible kinase 3 expression decreased markedly after CNE-2 cells were transfected with the serum- and glucocorticoid-inducible kinase 3 shRNA, leading to strong inhibition of cell proliferation and migration. In addition, the apoptosis rate increased in CNE-2 cells after serum- and glucocorticoid-inducible kinase 3 knockdown. Conclusion: Serum- and glucocorticoid-inducible kinase 3 expression was more frequently observed as the nasopharyngeal epithelium progresses from normal tissue to carcinoma. This suggests that serum- and glucocorticoid-inducible kinase 3 contributes to the multistep process of NPC carcinogenesis. Serum- and glucocorticoid-inducible kinase 3 represents a target for nasopharyngeal carcinoma therapy, and a basis exists for the further investigation of this adjuvant treatment modality for nasopharyngeal carcinoma.