Bortezomib is an efficient agent in plasma cell leukemias

Plasma cell leukemia (PCL) represents the most aggressive form of monoclonal gammopathy for which new treatment approaches are needed. Here we report the effect of Bortezomib on cells from 4 patients with PCL, as well as the in vivo efficacy on a patient with secondary PCL. Bortezomib reduced PCL numbers and was more efficient in cell growth inhibition than dexamethasone or doxorubicin. Treatment with Bortezomib induced procaspase-3 and poly(ADP-ribose) polymerase cleavage and decreased the amount of extracellular signal regulated kinase (Erk1/2) and phospho-Erk1/2. However, Bortezomib did not substantially affect the levels of the Erk1/2 upstream activating kinase (MEK1), p27 or p21. Finally, we had the opportunity to use Bortezomib in a heavily pretreated patient with overt secondary PCL and severe anemia and thrombocytopenia. Following Bortezomib treatment, circulating plasma cells disappeared; what is more striking, the peripheral blood counts returned to normal, becoming transfusion-independent. These data support the inclusion of Bortezomib in the therapeutic armamentarium of PCL.     

Proteasome inhibitors can alter the signaling pathways and attenuate the P-glycoprotein-mediated multidrug resistance

Numerous signaling pathways were reported to be involved in the resistance for conventional cytotoxic drugs, although one of the main reasons is the overexpression of P-glycoprotein (P-gp) in multidrug resistant cancer cells. The overexpression of P-gp has been associated with the resistance to a wide range of anticancer drugs. Doxorubicin and paclitaxel are substrates of this transporter system and have an important role for the various human malignancies. In the present study, drug-sensitive MCF7 and multidrug resistant MCF7/ADR (characterized by overexpression of P-gp) human breast cancer cell lines were used as an experimental model. We have found that PS341 and MG132, proteasome inhibitors, reduced the degree of the multidrug resistance (MDR) in MCF7/ADR cells. This phenomenon was accompanied by a decrease in the IC50 value of doxorubicin and paclitaxel from 55.9 +/- 3.46 to 0.60 +/- 0.08 microM, and from 17.61 +/- 1.77 to 0.59 +/- 0.12 microM, respectively. The IC50 values of sensitive cells for doxorubicin and paclitaxel were about 0.42 and 0.83 microM, respectively. The effect of PS341 and MG132 on MCF7/ADR cells was associated with a significant decrease in both protein and gene levels of P-gp expression. Moreover, with regard to the expression of possible signal transduction pathways of mitogen-activated protein kinase (MAPK) related to the activation of mdr1, proteasome inhibitors did significantly influence the activation of these proteins. Western blot analysis revealed that 24 hr exposure of multidrug resistant MCF7/ADR cells with proteasome inhibitors did change the levels of DNA binding activity of nuclear factor-kappaB (NF-kappaB), pERK1/2, c-Jun, and p-c-Jun. In conclusion, we could remark that proteasome inhibitors (especially PS341) attenuate the resistance of MCF7/ADR cells for P-gp substrate drugs of doxorubicin and paclitaxel. Several proteins are supposed to be associated with the resensitization of the cells to conventional cytotoxic drugs, although decreased activity of P-gp is at least involved in the proteasome inhibitor-related resensitization. And influence with MAPK pathways, which have been reported to be associated with the regulation of P-gp, might be contributed to the resensitization brought by proteasome inhibitors.     

Protein degradation during aging: the lysosome-, the calpain- and the proteasome-dependent cellular proteolytic systems

Aging is a natural process determined by both genetic and environmental factors. Aging is accompanied by the imbalance of the function of several cellular homeostatic mechanisms, which results, among others, in the accumulation of abnormal (i.e. oxidized, cross-linked, unfolded) proteins. It has been proposed that the increased failure of homeostasis during aging is due to the impaired function of the major cellular proteolytic mechanisms mediated by the lysosome, the calpains and the proteasome. This article will address the issue of the function of these cellular proteolytic systems during aging. This revised version was published online in July 2006 with corrections to the Cover Date.     

蛋白酶体抑制剂联合表阿霉素杀伤肝癌细胞的研究

目的观察蛋白酶体抑制剂MGl32与表阿霉素（epirubicin，EPI）联合应用对人肝癌HeDG2细胞系体外生长的影响。方法实验分为4组：空白对照组；1μg／mLEPI处理组；1μmol／LMGl32处理组；1／maol／LMGl32＋1μg／mLEPI共同处理组。应用MTT法检测小剂量MGl32与表阿霉素处理后对HepG2细胞的生长抑制作用，流式细胞术检测细胞凋亡。结果MTT法显示MGl32与表阿霉素合用时对HepG2细胞的抑制率增加。流式细胞术测定显示对照组的HepG2细胞凋亡率为（0．87±0．19）％，1μmol／LMGl32处理组细胞凋亡率为（5．53±0．99）％；1μg／mL EPI处理组细胞凋亡率为（13．8±1．37）％：1μmol／LMGl32和1μg／mL EPI共处理组细胞凋亡率增加至（27．0±1．15）％。结论小剂量MGl32与表阿霉素联合应用可增强致HepG2细胞凋亡作用。     

蛋白酶体抑制剂逆转肿瘤多药耐药的研究进展

肿瘤多药耐药是肿瘤治愈的主要障碍之一。肿瘤细胞对抗癌药物诱导的凋亡的耐受是多药耐药形成的重要原因。蛋白酶体抑制剂可选择性地促进肿瘤细胞凋亡，逆转多药耐药。蛋白酶体被认为是肿瘤治疗的新靶点。     

蛋白酶体及其抑制剂的研究进展

蛋白酶体抑制剂通过阻断泛素蛋白酶体通路,影响细胞内多个周期蛋白的降解,诱导细胞凋亡。体内外试验已显示蛋白酶体抑制剂具有广泛抗肿瘤作用。蛋白酶体抑制剂Bortezomib已通过美国FDA批准应用于临床治疗多发性骨髓瘤。该文就蛋白酶体结构、蛋白酶体抑制剂作用途径、促凋亡作用机制的研究成果和现阶段临床应用作一综述。     

Characterization of rabbit antisera elicited with human LMP2- and LMP7-specific peptides and recombinant proteins

Anti-human LMP2 and anti-human LMP7 sera with a titer of at least 1:10,000 were developed by immunizing rabbits with LMP2- and LMP7-specific peptides corresponding to C -terminal regions of each subunit or with TrxLMP2 and TrxLMP7 recombinant proteins. IgG antibodies elicited by immunization with LMP-specific peptides or recombinant proteins displayed reactivity with their respective immunogens in ELISA. Furthermore, antibodies elicited with both types of immunogens recognize native and recombinant LMP2 and LMP7 subunits in Western blotting and are able to immunoprecipitate LMP2 and LMP7 as components of the 20S proteasome from lymphoid cell lysates. In ELISA, a subpopulation of the antibodies generated with LMP peptides and recombinant proteins corresponding to one LMP subunit is cross-reactive with the other one. This antibody subpopulation was not detectable in the affinity-purified antibody populations isolated by passing antisera over the corresponding immunogen. Neither anti-LMP2 nor anti-LMP7 sera displayed cross-reactivity with the homologous proteasome subunits Delta and MB1. In immunohistochemical reactions affinity-purified anti-LMP2 and anti-LMP7 antibodies stained cells in both frozen and formalin-fixed tissue sections of normal skin. These results indicate that the anti-LMP2 and anti-LMP7 sera elicited with peptides and recombinant proteins are both useful reagents for biochemical characterization of LMP2 and LMP7 and to analyze their expression in normal and transformed cells.     

Adenovirus E4-34kDa requires active proteasomes to promote late gene expression

A complex of the Adenovirus (Ad) early region 1b 55-kDa protein (E1b-55kDa) and the early region 4 ORF6 34-kDa protein (E4-34kDa) promotes viral late RNA accumulation in the cytoplasm while inhibiting the transport of most newly synthesized cellular mRNA. The E4 ORF3 11-kDa protein (E4-11kDa) functionally compensates for at least some of the activities of this complex. We find that the same large central region of E4-34kDa that is required for proteasome-mediated degradation of p53 (J. Virol. 75, (2001) 699-709) is also required to promote viral late gene expression in a complementation assay. E4-34kDa does not promote late gene expression in complementation assays performed in the presence of proteasome inhibitors. A proteasome inhibitor also dramatically reduced late gene expression by a virus that lacks the E4-11kDa gene and therefore relies on E4-34kDa for late gene expression. Our results suggest that E4-34kDa activity in promoting late gene expression depends on the proteasome.     

3种新型蛋白酶体抑制剂对斑马鱼心脏毒性的评价

为了观察3种新型蛋白酶体抑制剂对斑马鱼的心脏毒性并初步探讨其机制,将斑马鱼胚胎分别暴露于一系列浓度的化合物NNU395、NNU458和NNU459。于显微镜下观察并拍摄斑马鱼的心脏形态,统计死亡率及心率,并检测斑马鱼心脏发育相关基因的表达情况。结果显示,NNU395、NNU458和NNU459呈浓度依赖地增加了斑马鱼的死亡率,对斑马鱼胚胎的半数致死浓度分别为(179.7±12.2),(27.5±1.3)和(24.4±2.6)μmol/L,且较之各自改构前体,3种化合物对斑马鱼的毒性更低。120~200 μmol/L NNU395及30 μmol/L的NNU458或NNU459处理后的斑马鱼出现明显的心包水肿和心脏畸形。120~200 μmol/L的NNU395及0.1~30 μmol/L的NNU458或10~30 μmol/L的NNU459均显著降低斑马鱼的心率。3种化合物对斑马鱼心脏发育相关基因的表达都没有显著影响。本研究提示低浓度的NNU395、NNU458和NNU459对斑马鱼心脏无明显毒性,高浓度的3种化合物对斑马鱼可产生心血管毒性。