The role of Pim-2 in apoptotic signal transduction pathway of hepatocellular carcinoma

Abstract

Background: Hepatocellular carcinoma (HCC) is one of the most frequent malignant tumors. The objective was to investigate the role of serine/threonine kinase Pim-2 in apoptosis signal transduction pathway, because there is little study about its contribution to apoptosis in hepatocellular carcinoma.Methods: The Pim-2 gene and protein expression were examined by qRT-PCR, Western blot and immunohistochemical stain in HCC tissues and normal liver tissues. The plasmid pCI-neo-Pim2 was transfected into human hepatoma cell line SMMC7721 by lipofectamine. Total RNAs were extracted from SMMC7721 cell in logarithm growth phase. The mRNA expression of Pim-2, Akt-1 (protein kinase B), 4E-BP1 (translation repressor of mammalian target of rapamycln), SOCS-1 (repressor of cytokine), Bad（Bcl-xL/Bcl-2 associated death promoter, Bim（Bc1-2 interacting mediator of cell death）and Puma (p53 upregulated modulator of apoptosis) were identified by qRT-PCR. The cell cycle of post-transfected SMMC7721 cells was assessed by flow cytometry.Results: Pim-2 expression was enhanced in HCC. In post-transfected SMMC7721 cells, Pim-2 mRNA expression was up-regulated, level of Bad mRNA was attenuated, furthermore, the transcription level of Akt-1, SOCS-1, 4E-BP1, Bim and Puma gene wasn’t variety. Up-graulated Pim-2 can’t cause distinct change of cell cycle or apoptosis in hepatoma cell.Conclusions: The serine/threonine kinase Pim-2 plays an import role in the development of HCC, Pim-2 dependent maintenance of cell size and survival correlated with its ability to maintain down-regulated expression of the BH3 protein Bad. Pim-2 is not a trigger in cell-autonomous survival or inhibiting apoptosis in hepatocellular carcinoma. Pim-2 is a redundancy pathway of survival signaling.