Wuxi Higher Health Vocational Technology School, Wuxi, Jiangsu, China.
Cancer Chemother Pharmacol. 2010 Aug;66(3):433-9. doi: 10.1007/s00280-009-1177-4. Epub 2009 Nov 24.
We have previously shown that the expression of glucosylceramide synthase (GCS) gene in drug-resistant K562/AO2 human leukemia cell was higher than that in drug-sensitive K562 cell, and the sensitivity to adriamycin of K562/AO2 cell was enhanced by inhibiting GCS. It is concluded that the overexpression of GCS gene is one of the reasons which lead to multidrug resistance (MDR) of leukemia cell. Meanwhile, we also found that higher expression of Bcl-2 gene and protein were exhibited in K562/AO2 cell compared with K562 cell. Basing on this, we hypothesized that the high expression of GCS gene which results in MDR of leukemia cell is correlated with Bcl-2 signal transduction. In order to validate the hypothesis, the inhibition of GCS gene in K562/AO2 cell was observed by using chemical suppressor PPMP and siRNA targeted at GCS, and applying RT-PCR and flow cytometry, the expression levels of apoptosis-related gene Bcl-2 and Bax were analyzed before and after inhibiting GCS gene in K562/AO2 cell. The results demonstrated that the gene and protein of Bcl-2 in K562/AO2 cell were both down-regulated significantly after GCS gene being inhibited; however, the Bax mRNA expression had no apparent change in different groups. This suggested that GCS gene may contributed to MDR of human leukemia cell K562/AO2 by Bcl-2 signal transduction.
我们之前已经表明，在耐药的 K562/AO2 人白血病细胞中，葡萄糖神经酰胺合酶（GCS）基因的表达高于在敏感的 K562 细胞中，并且通过抑制 GCS 可以增强 K562/AO2 细胞对阿霉素的敏感性。由此得出结论，GCS 基因的过表达是导致白血病细胞多药耐药（MDR）的原因之一。同时，我们还发现 K562/AO2 细胞中 Bcl-2 基因和蛋白的表达水平高于 K562 细胞。基于此，我们假设导致白血病细胞 MDR 的 GCS 基因的高表达与 Bcl-2 信号转导有关。为了验证这一假设，我们使用化学抑制剂 PPMP 和针对 GCS 的 siRNA 观察 K562/AO2 细胞中 GCS 基因的抑制情况，并通过 RT-PCR 和流式细胞术分析抑制 K562/AO2 细胞中 GCS 基因前后凋亡相关基因 Bcl-2 和 Bax 的表达水平。结果表明，抑制 GCS 基因后，K562/AO2 细胞中的 Bcl-2 基因和蛋白均显著下调；然而，不同组间 Bax mRNA 的表达没有明显变化。这表明 GCS 基因可能通过 Bcl-2 信号转导导致人白血病细胞 K562/AO2 的 MDR。
