抑瘤素M通过诱导衰老抑制肝癌细胞增殖

Inflammatory cytokine oncostatin M suppresses growth of liver cancer cells by inducing senescence

目的:通过分析抑瘤素M(oncostatin M,OSM)对肝癌细胞生长的效应,研究其影响细胞增殖的分子机制。方法:OSM处理SMMC-7721和Hep G2肝癌细胞系,观察细胞的增殖速率和形态变化,结合特异性β-半乳糖苷酶染色和细胞周期分析,研究OSM是否通过诱导肝癌细胞进入衰老状态来抑制其增殖;进一步通过监测细胞周期抑制蛋白p16、p21、p27和癌基因c-Myc的表达变化,分析OSM诱导细胞衰老的原因。结果:OSM可以抑制肝癌细胞系生长,且抑制率呈现一定剂量依赖性;细胞形态变化和β-半乳糖苷酶染色进一步证实OSM可诱导细胞衰老。细胞周期分析表明OSM阻滞肝癌细胞于G0/G1期,并伴随p21和p27周期抑制蛋白的表达增高。最后,通过分析STAT3信号途径下游癌基因c-Myc的转录与蛋白水平,表明OSM可能是通过癌基因的激活而诱导细胞的衰老。结论:由癌基因激活而导致的细胞衰老,是机体的一种防御机制。OSM通过激活STAT3信号途径、上调癌基因cMyc表达的同时,也加速了细胞的衰老,从而最终表现为对肝癌细胞增殖的抑制作用。

Objective： To provide a possible mechanism underlying oncostatin M （OSM）-induced tumor growth by investigating the effects on growth of liver cancer cells and its molecular pathway. Methods： Cell growth rates were analyzed after OSM treatment in human liver cancer cell lines-SMMC-7721 and HepG2. Cellular senescence based on growth arrest and morphologic phenotype of cells was detected by senescence-associated β-galactosidase （SA-β-gal） staining. Cell cycle profile was examined by flow cytometry. The ex- pression of key regulators of cell proliferation including cyclin-dependent kinase inhibitors （p16, p21, and p27） and c-Myc were analyzed at the level of mRNA and protein. Results： OSM suppressed cell proliferation in a dose-dependent manner. Upon drug treatment, morphological changes of cells notably implicated a senescent phenotype, which was further supported by the positive SA-β-gal staining. Meanwhile, OSM induced an increased proportion of cells at Go/G1 phase, which corresponded to the elevated expression of p21 and p27 at mRNA and protein levels. Unexpectedly, oncogene c-Myc was also dramatically upregulated upon OSM treatment. Conclusion： As a key regulator of cell proliferation and survival, c-Myc can be upregulated though the OSM-activated STAT3 pathway. While in short term, such hyperactive oncogene would induce cellular senescence as a barrier to transformation in cells with intact p53 machinery. These findings suggest that the elevated OSM during the earliest stages of liver cancer might serve as a tumor suppressor.