Gibalová Lenka, Sedlák Ján, Labudová Martina, Barancík Miroslav, Reháková Alena, Breier Albert, Sulová Zdena
Institute of Molecular Physiology and Genetics, Centre of Excellence of the Slovak Research and Development Agency BIOMEMBRANES 2008, Vlárska 5, 833 34 Bratislava, Slovakia.
Gen Physiol Biophys. 2009 Dec;28(4):391-403. doi: 10.4149/pb_2009_04_391.
P-glycoprotein (P-gp, a drug transporter found in the plasma membrane)-mediated multidrug resistance of leukemia cells represents a real obstacle in the effective chemotherapeutic treatment of leukemia. While cisplatin (CisPt) is known to be a substance that is untransportable by P-gp, P-gp positive cells were often found to be resistant to CisPt. The aim of the current paper is to study this phenomenon using P-gp positive mouse leukemia cells L1210/VCR in which the overexpression of P-gp was induced by its ability to adapt to growth on vincristine (VCR). L1210/VCR cells are also resistant to CisPt. However, resistance to this substance could not be reversed by addition of the known P-gp inhibitor verapamil. CisPt induced more pronounced entry into apoptosis, as measured using the annexin V/propidium iodide kit, in sensitive L1210 cells than in resistant L1210/VCR cells. In addition, CisPt induced an increase in the proportion of L1210 cells that were in the g2 phase of the cell cycle when compared to L1210/VCR cells, as measured by staining with propidium iodide. Similarly, a higher release of cytochrome c from the mitochondria to the cytosol was induced by CisPt treatment in L1210 than in L1210/VCR cells. While similar levels of Bax and Bcl-2 proteins were observed in sensitive and resistant cells, CisPt induced a more pronounced decrease of the Bcl-2 levels in L1210 cells than in L1210/VCR cells. Consistent with this observation, CisPt induced a larger decrease of the Bcl-2 content in the Bcl-2:Bax heterooligomer in L1210 cells than in L1210/VCR cells. Moreover, CisPt induced a similar apoptotic DNA fragmentation pattern in both resistant and sensitive cells. All of the above observations indicated that L1210/VCR cells are also resistant to CisPt and that this resistance is related to the differences in the regulatory mechanisms responsible for CisPt-induced apoptosis in L1210/VCR cells without any contribution from the drug efflux activity of P-gp.
P-糖蛋白（P-gp，一种存在于质膜中的药物转运蛋白）介导的白血病细胞多药耐药性是白血病有效化疗治疗中的一个实际障碍。虽然顺铂（CisPt）已知是一种不能被P-gp转运的物质，但经常发现P-gp阳性细胞对CisPt耐药。本文的目的是使用P-gp阳性小鼠白血病细胞L1210/VCR来研究这一现象，其中P-gp的过表达是由其适应长春新碱（VCR）生长的能力诱导的。L1210/VCR细胞也对CisPt耐药。然而，添加已知的P-gp抑制剂维拉帕米并不能逆转对该物质的耐药性。使用膜联蛋白V/碘化丙啶试剂盒检测发现，与耐药的L1210/VCR细胞相比，CisPt在敏感的L1210细胞中诱导更明显的细胞凋亡。此外，通过碘化丙啶染色测量，与L1210/VCR细胞相比，CisPt诱导L1210细胞处于细胞周期G2期的比例增加。同样，CisPt处理在L1210细胞中比在L1210/VCR细胞中诱导更多的细胞色素c从线粒体释放到细胞质中。虽然在敏感和耐药细胞中观察到相似水平的Bax和Bcl-2蛋白，但CisPt在L1210细胞中诱导的Bcl-2水平下降比在L1210/VCR细胞中更明显。与这一观察结果一致，CisPt在L1210细胞中诱导的Bcl-2:Bax异源寡聚体中Bcl-2含量下降比在L1210/VCR细胞中更大。此外，CisPt在耐药和敏感细胞中诱导了相似的凋亡DNA片段化模式。上述所有观察结果表明，L1210/VCR细胞也对CisPt耐药，并且这种耐药性与负责CisPt诱导L1210/VCR细胞凋亡的调节机制差异有关，而与P-gp的药物外排活性无关。
