Serum and glucocorticoid kinase 3 at 8q13.1 promotes cell proliferation and survival in hepatocellular carcinoma

Abstract

Amplification of broad regions of 8q is one of the most frequent genetic alterations in hepatocellular carcinoma (HCC), suggesting the existence of oncogenes in addition to MYC at 8q24.21. In this report we examine the potential role of the candidate amplified oncogene serum and glucocorticoid kinase 3 (SGK3) at 8q13.1 in HCC pathogenesis. We found amplification and overexpression of SGK3 was frequently detected in clinical HCC specimens and that SGK3 genomic activation was significantly associated with poor outcome of patients (P = 0.028). Functionally, we found that overexpression of SGK3 in HCC cells increased cell cycle progression through G(1), cell survival, clonogenicity, anchorage-independent growth, and tumor formation in nude mice. In contrast, RNA interference (RNAi) silencing of SGK3 inhibited its oncogenic effects. We provide evidence that SGK3 promotes HCC growth and survival through inactivating glycogen synthase kinase 3 beta and Bcl-2-associated death promoter, respectively. We also found that expression of SGK3, which like AKT is activated by PI3K/PDK1 signaling, has more significance than overexpression of AKT in predicting poor outcome in HCC patients. Taken together, our findings in the present study suggests that the SGK3 pathway may function in parallel with the AKT pathway and undergoes an AKT-independent signaling pathway in the pathogenesis of HCC. Further characterization of SGK3 may provide a prognostic biomarker for HCC outcome prediction and a novel therapeutic target in HCC treatment.