Altered expression of topoisomerase IIalpha contributes to cross-resistant to etoposide K562/MX2 cell line by aberrant methylation

KRN 8602 (MX2) is a novel morpholino anthracycline derivative having the chemical structure 3'-deamino-3'-morpholino-13-deoxo-10-hydroxycarminomycin hydrochloride. To investigate the mechanisms of resistance to MX2, we established an MX2-resistant phenotype (K562/MX2) of the human myelogeneous leukaemia cell line (K562/P), by continuously exposing a suspension culture to increasing concentrations of MX2. K562/MX2 cells were more resistant to MX2 than the parent cells, and also showed cross-resistance to etoposide and doxorubicin. Topoisomerase (Topo) IIalpha protein levels in K562/MX2 cells were lower of those in K562/P cells on immunoblot analysis and decreased expression of Topo IIalpha mRNA was seen in K562/MX2 cells. Topoisomerase II catalytic activity was also reduced in the nuclear extracts from K562/MX2 cells when compared with K562/P cells. Aberrant methylated CpG of Topo IIalpha gene was observed in K562/MX2 cells when compared with the parent line on methylation-specific restriction enzyme analysis. To overcome the drug resistance to MX2 and etoposide, we investigated treatment with 5-Aza-2'-deoxycytidine (5AZ), which is a demethylating agent, in K562/MX2 cells. 5-Aza-2'-deoxycytidine treatment increased Topo IIalpha mRNA expression in K562/MX2 cells, but not in K562/P cells, and increased the cytotoxicity of MX2 and etoposide. Methylated CpG was decreased in K562/MX2 cells after 5AZ treatment. We concluded that the mechanism of drug resistance to MX2 and etoposide in K562/MX2 cells might be the combination of decreased expression of Topo IIalpha gene and increased methylation, and that 5AZ could prove to be a novel treatment for etoposide-resistant cell lines, such as K562/MX2.     

Defective hepatic response to interferon and activation of suppressor of cytokine signaling 3 in chronic hepatitis C

BACKGROUND & AIMS: Approximately half of hepatitis C virus (HCV)-infected patients do not respond to current interferon (IFN)-alpha combination therapy. To understand IFN-alpha resistance in vivo, we examined the dynamic responses to both type I and type II IFNs, human IFN (hIFN)-alpha, -gamma, and consensus IFN, in the chimpanzee model. METHODS: Naive and HCV-infected chimpanzees were treated with 3 forms of hIFNs in vivo. Quantitative real-time polymerase chain reaction was performed to evaluate the expression of IFN-stimulated genes (ISGs) in both peripheral blood mononuclear cells and liver to compare the responses to hIFN between naive and infected chimpanzees. The hepatic expression of IFN signaling components and inhibitory regulators including suppressor of cytokine signaling 3 (SOCS3) were assessed. SOCS3 expression was also evaluated in the liver of HCV-infected patients undergoing IFN treatment. RESULTS: The in vivo responses to all 3 hIFNs were much lower in the HCV-infected chimpanzees than those in the naive chimpanzees. This defect was particularly evident in the liver because induction of hepatic ISGs was barely detectable in the infected animals. Following IFN administration, the expression of SOCS3 was significantly up-regulated, possibly through induction of interleukin-6, in the liver of HCV-infected chimpanzees. HCV-infected humans also showed a differential pattern of hepatic SOCS3 expression in response to IFN that is associated with treatment response. CONCLUSIONS: Our data indicate a predominantly defective hepatic response to IFN in HCV-infected chimpanzees, which is probably mediated through the activation of SOCS3 and may explain the nonresponse of many HCV patients to IFN-based therapy.     

Mechanisms underlying the anticancer activities of the angucycline landomycin E

Anthracyline antibiotics, produced by Streptomyces sp., still rank among the most efficient anticancer drugs in clinical use. Aim of this study was to gain deeper insight into the anticancer properties of the anthracycline-related angucycline landomycin E (LE). The impact of LE on nuclear morphology was assessed by 4',6-diamidino-2-phenylindole (DAPI) staining in the human carcinoma cell model KB-3-1. LE treatment led to the appearance of typical morphological signs of programmed cell death like cell shrinkage, chromatin condensation and formation of apoptotic bodies. Apoptotic cell death induced by LE was further characterised by caspase (substrate) cleavage and intense mitochondrial membrane depolarisation (JC-1 and rhodamine 123 staining) already after 1h drug incubation. Moreover, incubation with LE led to reduced intracellular ATP pools suggesting LE-induced apoptotic cell death as a consequence of rapid mitochondrial damage. Furthermore, LE treatment led to profound generation of intracellular oxidative stress, indicated by radical scavenger pre-treatment and dichlorofluorescin diacetate (DCF-DA) staining experiments. Since chemoresistance is a common problem in cancer therapy, we also investigated the influence of ABCB1 (P-glycoprotein, P-gp), ABCC1 (multidrug resistance-related protein, MRP1) and ABCG2 (breast cancer resistance protein, BCRP) overexpression on the anticancer activity of LE. Compared to anthracyclines, cytotoxic activity of LE was only weakly reduced by P-gp and MRP1 overexpression. Moreover, BCRP expression had no influence on LE anticancer activity. In summary, LE exerts anticancer activity via potent induction of apoptosis and has promising anticancer activity even against multidrug resistant (MDR) cells. Taken together, these data suggest further development of LE as a new anticancer drug.     

饮水氯化消毒副产物MX对人胚肝细胞(L-02)的DNA损伤及凋亡作用

目的　研究饮水氯化消毒副产物 3 氯 4 二氯甲基 5 羟基 2 (5氢 ) 呋喃酮 (MX)致人胚肝细胞 (L 0 2 )DNA损伤及凋亡作用。方法　以L 0 2为靶细胞 ,采用单细胞凝胶电泳技术 (SCGE)和流式细胞术 (FCM)分别检测MX致L 0 2细胞DNA损伤及凋亡作用。结果　随着MX浓度的增加 ,L 0 2细胞DNA链断裂逐渐增加 ,且 10 0和 30 0 μmol L剂量组与溶剂对照组相比具有统计学显著性差异 (P <0 0 5 ,P <0 0 1) ;MX各剂量组均引起L 0 2细胞凋亡率明显增加 ,与溶剂对照组相比具有统计学显著性差异 (P <0 0 0 1)。结论　饮水氯化消毒副产物MX可致L 0 2细胞DNA单链断裂和凋亡     

FreeHand MX在正常青年人侧面分析研究中的应用

目的：探讨正常青年人侧面外部软组织特征,探求FreeHand MX软件在侧面形态软组织测量分析中的实用性和可行性。方法：选择2010～20l2级在校学生（女生共65人,年龄20～22岁）,分别采用FreeHand Mx软件和Photoshop软件对青年学生颜面侧貌外部软组织进行测量分析。结果：通过两种软件获得反映侧面形态比例的∠α、∠β、∠γ及反映鼻唇颏协调性的∠Z之间无明显差别;采用FreeHandMX软件,应用不同标准筛选出65名女生面侧貌中符合ESR标准的∠α、∠β、∠γ、∠Z4项均值。结论：应用FreeHandMx软件对侧面外部软组织测量分析,体现了软件的实用性和可行性;对面侧貌审美时应把以耳屏中点为圆心,耳屏中点到鼻尖的距离为半径的圆所经过发缘点、软组织鼻尖点、软组织颏前点的弧线纳入审美标准中,对评价和分析侧面貌更具有效性。本测量结果为美学、整形外科学等领域实施手术治疗制定提供理论依据,为疗效评价提供定量参考依据。     

心血管疾病抗血栓的新靶点P2Y12受体

阿司匹林的应用降低了心血管疾病的病死率和发病率。但其有限的抗血小板效果及近来发现的阿司匹林抵抗现象驱使人们寻找更有效的抗血小板药物。噻氯匹啶和氯吡格雷，通过其代谢产物作用于血小板ADP受体亚基，目前称为P2Y12（过去称P2T，P2TAC，P2YADP或P2Ycyc）受体拮抗剂，显示了很好的临床疗效。天然的P2Y12受体拮抗剂ATP有快速而直接的作用。AR—C69931MX，就是类似A仰的一种拮抗剂。对ADP诱导的血小板活化、聚集、分泌凝血活性物质有抑制作用。Ⅱ期临床研究显示在急性冠脉综合征的患者注射AR—C69931MX能获得快速稳定的血小板聚集抑制作用，t1/2仅几分钟。血小板糖蛋白GPⅡb／Ⅲa拮抗剂临床应用的局限性给这些抗血小板药物提供了很好的发展前景。     

Flash MX制作"线粒体遗传病"网络课件的研究

介绍了如何用Flash MX制作“线粒体遗传病”的网络课件，以及其中制作的技巧。     

Cangrelor: a novel P2Y12 receptor antagonist

Antiplatelet therapy is critical in the prevention of thrombotic complications of acute coronary syndrome and percutaneous coronary interventions. Current antiplatelet agents (aspirin, clopidogrel and glycoprotein IIb/IIIa antagonists) have demonstrated the capacity to reduce major adverse cardiac events. However, these agents have limitations that compromise their clinical utility. The platelet P2Y₁₂ receptor plays a central role in platelet function and is a focus in the development of antiplatelet therapies. Cangrelor is a potent, competitive inhibitor of the P2Y₁₂ receptor that is administered by intravenous infusion and rapidly achieves near complete inhibition of ADP-induced platelet aggregation. This investigational drug has been studied for use during coronary procedures and the management of patients experiencing acute coronary syndrome and is undergoing evaluation for use in the prevention of perioperative stent thrombosis.