Department of Molecular Biology of Cancer, Medical University of Lodz, Lodz, Poland.
Br J Pharmacol. 2009 Aug;157(8):1451-62. doi: 10.1111/j.1476-5381.2009.00333.x. Epub 2009 Jul 20.
Several anticancer drugs with diverse chemical structures can induce differentiation of cancer cells. This study was undertaken to explore the potential contribution of caspase-3 to pharmacologically-induced differentiation of K562 cells.
We assessed differentiation by measuring the expression of glycophorin A and haemoglobin synthesis in K562 cells treated with low concentrations of doxorubicin, hydroxyurea, cytosine arabinoside, cisplatin and haemin. Caspase-3 activation, mitochondrial membrane potential dissipation and viability were assessed by FACS. GATA-1-binding activity was evaluated by EMSA.
Treatment of K562 cells with low concentrations of the tested drugs activated caspase-3 but did not trigger detectable apoptosis. Instead, elevated levels of haemoglobin-positive and glycophorin A/caspase-3-double-positive cells were observed, suggesting involvement of caspase-3 in drug-induced differentiation. Inhibition of caspase-3 activity significantly reduced the ability of K562 cells to execute the differentiation programme. Mitochondrial membrane potential dissipation was observed, indicating involvement of the mitochondrial pathway. Binding activity of GATA-1, transcription factor responsible for differentiation and cell survival, was not diminished by increased caspase-3 activity during drug-stimulated differentiation.
Our results could explain how anticancer drugs, with diverse structures and modes of action, can stimulate erythroid differentiation in leukaemic cells with appropriate genetic backgrounds. Our findings imply that some similarities exist between pharmacologically-induced differentiation of erythroleukaemic cells and normal erythropoiesis, both involving caspase-3 activation at high levels of anti-apoptotic protein Bcl-X(L) and chaperone protein Hsp70 (heat shock protein 70). Therefore, the functions of caspase-3, unrelated to cell death, can be extended to pharmacologically-induced differentiation of some cancer cells.
多种化学结构的抗癌药物可诱导癌细胞分化。本研究旨在探讨 caspase-3 在低浓度阿霉素、羟基脲、胞嘧啶阿拉伯糖苷、顺铂和血红素诱导 K562 细胞分化中的潜在作用。
通过测量 K562 细胞中糖蛋白 A 的表达和血红蛋白合成来评估分化。用 FACS 检测 caspase-3 激活、线粒体膜电位耗散和细胞活力。用 EMSA 评估 GATA-1 结合活性。
用低浓度的测试药物处理 K562 细胞可激活 caspase-3，但不会引发可检测的细胞凋亡。相反，观察到血红蛋白阳性和糖蛋白 A/caspase-3 双阳性细胞的水平升高，表明 caspase-3 参与药物诱导的分化。抑制 caspase-3 活性显著降低了 K562 细胞执行分化程序的能力。观察到线粒体膜电位耗散，表明涉及线粒体途径。负责分化和细胞存活的转录因子 GATA-1 的结合活性并未因药物刺激分化过程中 caspase-3 活性的增加而降低。
我们的结果可以解释为什么具有不同结构和作用机制的抗癌药物可以在具有适当遗传背景的白血病细胞中刺激红细胞分化。我们的发现表明，在药理学诱导的红白血病细胞分化和正常红细胞生成之间存在一些相似之处，两者都涉及 caspase-3 在高水平抗凋亡蛋白 Bcl-X(L) 和伴侣蛋白 Hsp70（热休克蛋白 70）的激活。因此，与细胞死亡无关的 caspase-3 的功能可以扩展到某些癌细胞的药理学诱导分化。
