Glioma-derived mutations in isocitrate dehydrogenase 2 beneficial to traditional chemotherapy

Heterozygous mutations in either the R132 residue of isocitrate dehydrogenase I (IDH1) or the R172 residue of IDH2 in human gliomas were recently highlighted. In the present study, we report that mutations of IDH1 and IDH2 are not detected in the rat C6 glioma cell line model, which suggests that these mutations are not required for the development of glioblastoma induced by N,N′-nitroso-methylurea. The effects of IDH2 and IDH2^R172G on C6 cells proliferation and sensitivity to chemotherapy and the possible mechanism are analyzed at the cellular level. IDH1 and IDH2 mutations lead to simultaneous loss and gain of activities in the production of α-ketoglutarate (α-KG) and 2-hydroxyglutarate (2HG), respectively, and result in lowering NADPH levels even further. The low NADPH levels can sensitize tumors to chemotherapy, and account for the prolonged survival of patients harboring the mutations. Our data extrapolate potential importance of the in vitro rat C6 glioma cell model, show that the IDH2^R172G mutation in gliomas may give a benefit to traditional chemotherapy of this cancer and serve as an important complement to existing research on this topic.     

低强度超声促进放疗后犬下颌种植体骨结合的实验研究

目的：探讨放射线损伤犬的下颌骨行种植术后,低强度超声是否对其周围骨组织结合具有促进作用。方法：建立下颌骨放射线损伤的动物模型,并运用低强度超声对其进行治疗,通过Micro—CT、拔出实验等观察低强度超声治疗组（实验II组）与未用低强度超声治疗组（实验I组）,并与对照组对比,所得数据进行统计学分析。结果：成功的建立了放射线损伤的动物模型;实验II组骨小梁的各项指标均好于实验I组;拔出实验结果显示,实验II组拔出力值明显大于实验I组。统计结果显示各组之间的差异具有显著性的意义（P〈0．05）。结论：低强度超声对放射线照射后种植体周围的骨组织具有较好的修复作用     

Noxa/Bcl-2 protein interactions contribute to bortezomib resistance in human lymphoid cells

Previous studies have suggested that the BH3 domain of the proapoptotic Bcl-2 family member Noxa only interacts with the anti-apoptotic proteins Mcl-1 and A1 but not Bcl-2. In view of the similarity of the BH3 binding domains of these anti-apoptotic proteins as well as recent evidence that studies of isolated BH3 domains can potentially underestimate the binding between full-length Bcl-2 family members, we examined the interaction of full-length human Noxa with anti-apoptotic human Bcl-2 family members. Surface plasmon resonance using bacterially expressed proteins demonstrated that Noxa binds with mean dissociation constants (K(D)) of 3.4 nm for Mcl-1, 70 nm for Bcl-x(L), and 250 nm for wild type human Bcl-2, demonstrating selectivity but not absolute specificity of Noxa for Mcl-1. Further analysis showed that the Noxa/Bcl-2 interaction reflected binding between the Noxa BH3 domain and the Bcl-2 BH3 binding groove. Analysis of proteins expressed in vivo demonstrated that Noxa and Bcl-2 can be pulled down together from a variety of cells. Moreover, when compared with wild type Bcl-2, certain lymphoma-derived Bcl-2 mutants bound Noxa up to 20-fold more tightly in vitro, pulled down more Noxa from cells, and protected cells against killing by transfected Noxa to a greater extent. When killing by bortezomib (an agent whose cytotoxicity in Jurkat T-cell leukemia cells is dependent on Noxa) was examined, apoptosis was enhanced by the Bcl-2/Bcl-x(L) antagonist ABT-737 or by Bcl-2 down-regulation and diminished by Bcl-2 overexpression. Collectively, these observations not only establish the ability of Noxa and Bcl-2 to interact but also identify Bcl-2 overexpression as a potential mechanism of bortezomib resistance.