Protein kinase C-ε promotes survival of lung cancer cells by suppressing apoptosis through dysregulation of the mitochondrial caspase pathway
Protein kinase C-ε promotes survival of lung cancer cells by suppressing apoptosis through dysregulation of the mitochondrial caspase pathway
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DOI：
10.1074/jbc.m201460200
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发表时间：
2002-09-20
影响因子：
4.8
通讯作者：
Xiao, L
中科院分区：
文献类型：
--
作者：
Ding, L;Wang, HM;Xiao, L
丝氨酸/苏氨酸蛋白激酶C（PKC）在许多类型癌细胞的耐药性和细胞存活的调节中都有涉及。然而，一种或多种确切机制仍不清楚。在这项研究中，我们已经确定并阐明了一种新型PKC异构体PKC - ε调节肺癌细胞耐药性的机制。蛋白质印迹分析表明，PKC - ε（而非其他PKC异构体）的表达与非小细胞肺癌（NSCLC）细胞系的耐药表型相关。Northern杂交和核连缀转录分析进一步揭示，小细胞肺癌（SCLC）细胞敏感表型中PKC - ε表达缺失是由于该基因转录失活所致。重要的是，在NCI - H82人SCLC细胞中强制表达PKC - ε使其对化疗药物依托泊苷和阿霉素产生显著耐药性。耐药性的特征是表达PKC - ε的细胞凋亡显著减少。用依托泊苷处理NCI - H82细胞会诱导一系列时间依赖性事件，包括细胞色素c从线粒体释放到细胞质、半胱天冬酶 - 9和半胱天冬酶 - 3的激活以及多聚（ADP - 核糖）聚合酶（PARP）的裂解。所有这些事件都被PKC - ε的表达所阻断。此外，半胱天冬酶特异性抑制剂z - VAD - fmk和z - DEVD - fmk显著减弱亚G₁期细胞群的积累，并阻断依托泊苷诱导的PARP裂解。这些结果表明，PKC - ε通过抑制线粒体依赖性半胱天冬酶激活来阻止细胞凋亡，从而导致细胞存活。最后，在NSCLC细胞中通过反义cDNA下调PKC - ε的表达会导致对依托泊苷的敏感性增加。综上所述，我们的研究结果表明PKC - ε在调节肺癌细胞存活方面具有重要作用。
The serine/threonine protein kinase C (PKC) has been implicated in the regulation of drug resistance and cell survival in many types of cancer cells. However, the one or more precise mechanisms remain elusive. In this study, we have identified and determined the mechanism by which PKC-epsilon, a novel PKC isoform, modulates drug resistance in lung cancer cells. Western blot analysis demonstrates that expression of PKC-epsilon, but not other PKC isoforms, is associated with the chemo-resistant phenotype of non-small cell lung cancer (NSCLC) cell lines. Northern blotting and nuclear run-on transcription analysis further reveals that the failure of expression of PKC-epsilon in the chemo-sensitive phenotype of small cell lung cancer (SCLC) cells results from transcriptional inactivation of the gene. Importantly, forced expression of PKC-epsilon in NCI-H82 human SCLC cells confers a significant resistance to the chemotherapeutic drugs, etoposide and doxorubicin. Resistance is characterized by a significant reduction in apoptosis in PKC-epsilon-expressing cells. Treatment of NCI-H82 cells with etoposide induces a series of time-dependent events, including the release of cytochrome c from the mitochondria to the cytosol, activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase (PARP). All of these events are blocked by PKC-epsilon expression. Furthermore, caspase-specific inhibitors, z-VAD-fink and z-DEVD-fmk, significantly attenuate the accumulation of sub-G(1) population and block the PARP cleavage in response to etoposide. These results suggest that PKC-epsilon prevents cells from undergoing apoptosis through inhibition of the mitochondrial-dependent caspase activation, thereby leading to cell survival. Finally, down-regulation of PKC-epsilon expression by the antisense cDNA in NSCLC cells results in increased sensitivity to etoposide. Taken together, our findings suggest an important role for PKC-epsilon in regulating survival of lung cancer cells.