Lethal Effect of Benzene Nitrogen Mustard Glucoside Derivate on K562 Cells

A new synthesized benzene nitrogen mustard was converted into glycosyl donor-trichloroacetimidate that was glycosylated with p-nitrophenol（glycosyl donors） to form β-lactosyl p-nitrobenzene under the protection of acetyl in a stereoselective manner, was prepared and evaluated for its cytotoxicity towards cultured K562 cell line. Methylthiazoy tetrazolium（MTT） assay, transmission electron microscopy（TEM）, flow cytometry（FCM） and immunohistochemistry were utilized to explore the mechanisms of how the compound arrests the growth of HCT-T cells. This new synthesed benzene nitrogen mustard glucoside derivate（BNMGD） presented a lower toxicity to normal cells, but is significantly more toxic to K562 cells compared with nitrogen mustard, meanwhile it can induce the apoptosis of K562 cells. These results indicate that the new synthesized BNMGD can inhibit the growth of K562 cells and induce the apoptosis, and its cytotoxicity towards cultured K562 cell line is much more effective than that of nitrogen mustard.

Expression of Histone H2AX Phosphorylation and Its Potential to Modulate Adriamycin Resistance in K562/A02 Cell Line

DNA repair processes play a role in the development of drug resistance which represents a huge obstacle to leukemia chemotherapy. Histone H2AX phosphorylation （ser139） （γH2AX） occurs rapidly at the onset of DNA double strand break （DSB） and is critical to the regulation of DSB repair. If DNA repair is successful, cells exposed to anti-neoplastic drugs will keep entering the cycle and develop resistance to the drugs. In this study, we investigated whether γH2AX can be used as an indicator of tumor chemosensitivity and a potential target for enhancing chemotherapy. K562 and multi-drug resistant cell line K562/A02 were exposed to adriamycin （ADR） and γH2AX formed. Flow cytometry revealed that percentage of cells expressing γH2AX was increased in a dose-dependent manner and the percentage of K562/A02 cells was lower than that of K562 cells when treated with the same concentration of ADR. In order to test the potential of γH2AX to reverse drug resistance, K562/A02 cells were treated with PI3K inhibitor LY294002. It was found that LY249002 decreased ADR-induced γH2AX expression and increased the sensitivity of K562/A02 cells to ADR. Additionally, the single-cell gel electrophoresis assay and the Western blotting showed that LY249002 enhanced DSBs and decreased the expression of repair factor BRCA1. These results illustrate chemosensitivity can partly be measured by detecting γH2AX and drug resistance can be reversed by inhibiting γH2AX.

HSP70高表达对K_(562)细胞化疗敏感性研究

目的 研究化学因素引起的热应激蛋白 70 (HSP70 )升高对K56 2 细胞化疗药物体外敏感性的影响。方法用氯化镉诱导K56 2 细胞使其HSP70高表达 ,在高表达细胞中分别加入甲氨蝶呤 (MTX)、丝裂霉素C(MitomycinC)、顺氯氨铂 (PDD)、平阳霉素 (Bleomycin)等 4种化疗药物 ,药物浓度以临床一次用量的 1/ 2 5 0为中剂量 ,中剂量的 1/ 10、10倍分别为低剂量和高剂量 ,作用 16h后用MTT比色法检测细胞活力 ;HSP70用RT -PCR检测。结果 氯化镉可诱导细胞HSP70高表达 ,其中作用 4h后表达最高 ;HSP70高表达可以降低细胞对化疗药物的敏感性 ,HSP70表达水平越高 ,细胞对化疗药物的敏感性越低。结论 非热诱导的HSP70高表达可以降低肿瘤细胞对化疗药物的敏感性 。

超声对人红白血病细胞系K_(562)作用的研究

超声对人红白血病细胞系Ｋ５６２作用的研究齐浩１马玉英２谭声江１宋存牛２（１陕西师范大学生命科学学院，西安７１００６２；２陕西师范大学应用声学研究所，西安７１００６２；第一作者，女，４２岁，讲师）光动力学（ＰＤＴ）问世以来，实验已证实超声（ＵＳ）也可激...

Reversal effect of bufalin on multidrug resistance in K562/VCR vincristine-resistant leukemia cell line

OBJECTIVE: To probe insights into the reversal effect of bufalin on vincristine-acquired multidrug resistance(MDR) in human leukemia cell line K562/VCR.METHODS: Proliferative inhibition rate and the reversal index(RI) of bufalin were determined by Methyl thiazolyl tetrazolium assay. The uptake of Adriamycin(ADM) in K562/VCR cells, cell cycle and apoptosis rate were determined by flow cytometry(FCM). Cell morphologic changes were observed with Wright-Giemsa staining. The expression of P-glycoprotein(P-gp), multidrug-associated protein-1(MRP1), Bcl-x L and Bax protein were measured by immunocytochemistry.RESULTS: The human leukemia multidrug resistant K562/VCR cells showed no cross-resistance to bufalin. The RIs of bufalin at concentrations of 0.0002,0.001 and 0.005 μmol/L were 4.85, 6.94 and 14.77,respectively. Preincubation of 0.001 μmol/L bufalin for 2 h could increase intracellular ADM fluorescence intensity to 28.07%(P<0.05) and down-regulate MRP1 expression simultaneously, but no remarkable effect was found on P-gp protein. Cell cycle analysis indicated increased apoptosis rate and apparent decreased G2/M phase proportion after treatment with bufalin. When exposed to 0.01μmol/L bufalin, typical morphological changes of apoptosis could be observed. Down-regulation of Bcl-x L and up-regulation of Bax expression in K562/VCR cells could be detected by immunocytochemistry.CONCLUSION: Bufalin could partly reverse the MDR of K562/VCR cells, with a possible mechanism of down-regulating MRP1 expression and activating apoptosis pathway by altering Bcl-x L/Bax ratio.

Effect of polo-like kinase 1 gene silence on cell cycle and drug resistance in K562/A02 cell

Polo-like kinase 1（PLK1） plays an important role in many cell-cycle-related events. At G2/Mtransition, PLK1 contributes to the activation of cyclinB/Cdc by phosphorylation of Cdc25C, centrosome functional maturation, bipolar spindle formation. In later stage of mitosis, PLK1 is involved in regulating components of the anaphase-promoting complex （APC） for mitotic exit and in the execution of cytokinesis. Moreover, recent reports have shown that PLK1 is involved in both G2 and mitotic DNA damage checkpoints. When G2/M DNA damage occurs, PLK1 activity is suppressed and cell cycle arrests to repair the damaged DNA. So far, the deregulated expression of PLK1 has been detected in many types of human tumors and PLK1 is considered as a novel prognostic marker for several tumors.

Curcumin Prevents Induced Drug Resistance:A Novel Function?

Objective：We supposed that it will be a promising strategy to ＂prevent＂ multidrug resistance （MDR） instead of ＂reversing＂ it.This study was designed to investigate the potency of curcumin to prevent the acquired drug resistance induced by adriamycin （ADM） in native K562 cells.Methods：K562 cells were pretreated with curcumin or 0.5% DMSO for 24 h and then were co-incubated with ADM.P-glycoprotein （P-gp） and mdr1 mRNA levels were analyzed separately by flow cytometry and quantitative real-time RT-PCR.The intracellular Rh-123 accumulation was also detected by flow cytometer.Finally,we performed a MTT assay to determine the ADM-induced cytotoxicity with or without pretreatment of curcumin.Results：P-gp and mdr1 mRNA expressions were elevated in the ADM alone group.While in the curcumin pretreated groups,the induced P-gp and mdr1 mRNA levels gradually decreased with increasing curcumin concentrations,and the Rh-123 accumulation level was almost recovered close to the control group＇s.Finally,the MTT colorimetric assay verified the enhanced effect of curcumin on ADM-induced cytotoxicity.Conclusion：Our present study suggested that curcumin exhibits the novel ability to prevent the up-regulation of P-gp and its mRNA induced by ADM.The prevention capacity is also functionally associated with the elevated intracellular drug accumulation and parallel enhanced ADM cytotoxicity.We revealed a novel function of curcumin as a potential drug resistance preventor.

硒酸酯多糖和亚硒酸钠抗白血病效应的实验研究

应用ＭＴＴ比色分析法和细胞克隆形成法比较研究了有机硒化物－硒酸酯多糖和无机硒物－亚硒酸钠对白血病Ｋ５６２细胞的作用。结果表明：ＫＳＣ和Ｎａ２ＳｅＯ３体外在实验浓度范围内均对Ｋ５６２细胞的增殖具有显著的抑制作用，并有剂量反应；Ｋ５６２细胞具有我更新能力的细胞群体对硒的抑制作用更敏感；ＫＳＣ的抗白血病效应明显高于含同样硒量的Ｎａ２ＳｅＯ３，ＫＳＣ的作用约为Ｎａ２ＳｅＯ３的５倍。