Gong Jianping, Wang Jinjing, Ren Ke, Liu Chang'an, Li Bo, Shi Yujun
Department of General Surgery, 2nd College of Clinical Medicine, 2nd Affiliated Hospital of Chongqing University of Medical Science, Chongqing, China.
J Surg Res. 2009 May 1;153(1):17-22. doi: 10.1016/j.jss.2008.03.033. Epub 2008 Apr 22.
It has been proven that serine/threonine kinase pim-2 mediates cell survival and prevents apoptosis in hematopoietic system tumors and lymphomas, but its role in solid organ tumor induction is still unclear. In this study, we investigated its effects and underlying mechanisms in tumorigenesis of hepatocellular carcinoma.
We first examined the pim-2 gene expression and its protein levels in human hepatocellular carcinoma, paired noncancerous liver, and normal liver tissues. Then, we cultured human liver cancer cells and immortalized liver cells to examine the effects of pim-2 gene on the cell viability, growth, and apoptosis in different culture conditions. For further investigation of the molecular events in the pim-2 signal pathway, we also explored pim-2 kinase activity on phosphorylation of the two downstream signal mediators: 4E-BP1 and Bad.
Pim-2 gene and protein were notably expressed in human liver cancer tissues and HepG2 cells. The ectopic pim-2 overexpressing L02 cells were able to survive in interleukin-3 (IL-3)-deprived circumstance but not in glucose-free medium. Compared with HepG2 cells, pim-2 knock-down HepG2 cells lost survival ability in IL-3 starvation medium. In pim-2-expressing cells, both the total protein expressions of 4E-BP1 and Bad were kept stable; however, their phosphorylated patterns were notably increased.
Our results indicate that pim-2 acts as a pro-survival kinase to inhibit apoptosis and keep liver cell survival in IL-3-deprived medium. Pim-2 might participate in the tumorigenesis of hepatocellular carcinoma induction through its downstream molecules 4E-BP1 and Bad.
已证实丝氨酸/苏氨酸激酶pim-2介导造血系统肿瘤和淋巴瘤中的细胞存活并预防细胞凋亡，但其在实体器官肿瘤发生中的作用仍不清楚。在本研究中，我们调查了其在肝细胞癌发生中的作用及其潜在机制。
我们首先检测了人肝细胞癌、配对的癌旁肝组织和正常肝组织中pim-2基因表达及其蛋白水平。然后，我们培养人肝癌细胞和永生化肝细胞，以检测pim-2基因在不同培养条件下对细胞活力、生长和凋亡的影响。为了进一步研究pim-2信号通路中的分子事件，我们还探讨了pim-2激酶对两种下游信号介质4E-BP1和Bad磷酸化的活性。
pim-2基因和蛋白在人肝癌组织和HepG2细胞中显著表达。异位过表达pim-2的L02细胞能够在缺乏白细胞介素-3（IL-3）的环境中存活，但不能在无葡萄糖培养基中存活。与HepG2细胞相比，敲低pim-2的HepG2细胞在IL-3饥饿培养基中丧失了存活能力。在表达pim-2的细胞中，4E-BP1和Bad的总蛋白表达均保持稳定；然而，它们的磷酸化模式显著增加。
我们的结果表明，pim-2作为一种促存活激酶，在缺乏IL-3的培养基中抑制细胞凋亡并维持肝细胞存活。Pim-2可能通过其下游分子4E-BP1和Bad参与肝细胞癌的发生。
