G1 phase-dependent expression of Bcl-2 mRNA and protein correlates with chemoresistance of human cancer cells
G1 phase-dependent expression of Bcl-2 mRNA and protein correlates with chemoresistance of human cancer cells
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DOI：
10.1124/mol.58.5.1001
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发表时间：
2000-11-01
影响因子：
3.6
通讯作者：
Dou, QP
中科院分区：
文献类型：
--
作者：
Gao, G;Dou, QP
最近的实验表明，细胞增殖和程序性细胞死亡（凋亡）之间的相互联系，但详细的分子机制仍不清楚。我们假设一些凋亡调节因子的表达是细胞周期依赖性的，这反过来又以细胞周期依赖性的方式影响肿瘤细胞的化疗敏感性。为了验证这些假设，我们同步人类白血病Jurkat T，Neo（使用aphidicolin），乳腺癌MCF-7，正常成纤维细胞和猿猴病毒40转化细胞（通过aphidicolin或血清饥饿），并测量几种Bcl-2家族蛋白的水平。Bcl-2蛋白在G1期表达最高。相反，Bax蛋白水平在四种细胞系中保持相对不变，并且Bcl-X-L、Bcl-X-S和巴克蛋白水平在Jurkat T细胞中显示很少或没有细胞周期依赖性变化。与Bcl-2蛋白水平的变化类似，其mRNA表达也是G（1）期特异性的，而Bcl-2切割活性的水平保持组成性。当用抗癌药物（依托泊苷或顺铂）或激酶抑制剂星形孢菌素处理时，含有高G（1）群体和高Bcl-2蛋白水平的细胞比含有高S期群体和低Bcl-2蛋白水平的细胞对诱导的凋亡更有抵抗力。在Jurkat T细胞中Bcl-2蛋白的组成性过表达完全阻断了S期相关的对这些凋亡刺激的敏感性。细胞周期依赖性Bcl-2蛋白表达可能参与调节肿瘤细胞的化疗敏感性和凋亡定向。
Recent experiments suggest an interconnection between cell proliferation and programmed cell death (apoptosis), although the detailed molecular mechanisms remain unclear. We have hypothesized that expression of some apoptosis regulators is cell cycle-dependent, which in turn influences tumor cell chemosensitivity in a cell cycle-dependent fashion. To test these hypotheses, we synchronized human leukemia Jurkat T, Neo (using aphidicolin), breast cancer MCF-7, normal fibroblast, and simian virus 40-transformed cells (by aphidicolin or serum starvation), and measured levels of several Bcl-2 family proteins. The highest expression of Bcl-2 protein was found in the G(1) phase of all the five cell lines tested. In contrast, levels of Bax protein remained relatively unchanged in four of the cell lines, and levels of Bcl-X-L, Bcl-X-S, and Bak proteins showed little or no cell cycle-dependent changes in Jurkat T cells. Similar to the changes in Bcl-2 protein levels, its mRNA expression was also G(1) phase-specific, whereas the level of a Bcl-2 cleavage activity remained constitutive. When treated with an anticancer drug (etoposide or cisplatin) or the kinase inhibitor staurosporin, the cells containing a high G(1) population and a high Bcl-2 protein level were much more resistant to the induced apoptosis than the cells containing a high S phase population and a low Bcl-2 protein level. Constitutive overexpression of Bcl-2 protein in Jurkat T cells completely blocked the S phase-associated sensitivity to these apoptosis stimuli. The cell cycle-dependent Bcl-2 protein expression seems to contribute to the regulation of chemosensitivity and apoptotic commitment of human tumor cells.