以Hsp90为靶点治疗真菌感染的研究进展和展望

为了增强抗真菌药物的效能并避免真菌耐药,以分子伴侣Hsp90作为药物靶点是一个新的有前途的策略。对于系统性真菌感染,如果想要达到有效的联合用药效果,就需选择对病原真菌Hsp90有特异性作用的抑制剂。本文总结了Hsp90与病原真菌耐药的关系和对真菌毒力特征的调节,Hsp90功能的调节及其客户蛋白,并讨论了为治疗真菌感染而研发Hsp90抑制剂所面临的挑战。     

Hsp90抑制剂的研究进展

热激蛋白90(heat shock protein90,Hsp90)作为分子伴侣在调节细胞生长、分化、凋亡等方面发挥着重要的作用。Hsp90抑制剂能与Hsp90结合,使其功能丧失,造成细胞的多种生理活动缺陷,在Hsp90功能研究和癌症治疗方面具有潜在的价值。综述了不同来源的Hsp90抑制剂及其作用机制,同时对新型Hsp90抑制剂的来源进行了探讨。     

热激蛋白90抑制剂

分子伴侣热激蛋白90(heat-shock protein 90,Hsp90)在生物体内具有重要的生理功能,它在许多肿瘤细胞中表达增加。临床研究发现Hsp90抑制剂单一用药或者联合用药都具有较好的抗肿瘤效果,因此目前Hsp90被认为是癌症治疗一个非常有潜力的靶标。本文总结了Hsp90的结构功能、Hsp90抑制剂的作用机理以及Hsp90抑制剂的临床应用前景,希望为设计和开发新的Hsp90抑制剂提供一定的参考。     

以EGFR为靶点的肿瘤分子靶向药物研究进展

随着分子生物学研究的进展,分子靶向治疗已成为除手术、放疗、化疗之外的第4种治疗方法,越来越多的用于临床治疗恶性肿瘤。分子靶向药物进入体内能够特异地选择致癌位点,杀伤肿瘤细胞,而不会波及周围正常的组织细胞,因此分子靶向治疗又被称为"生物导弹"。与传统化疗药物相比,分子靶向药物具有特异性强、疗效明显、副作用少等优点。按照分子靶向药物的性质主要归为两大类:一类是单克隆抗体,如西妥昔单抗等;另一类是单靶点或多靶点的小分子抑制剂,如吉非替尼等。表皮生长因子受体(EGFR)对肿瘤的生长、发展以及肿瘤干细胞的维持都有着非常重要的作用,并且在多种实体瘤中存在过表达或异常表达,因此在肿瘤治疗中,EGFR成为一个非常重要的用药靶点。现主要对目前国内已上市的针对EGFR的分子靶向药物最新的临床研究进展作一简要综述。     

卵巢癌的靶向药物治疗研究进展

卵巢癌死亡率居女性生殖系统恶性肿瘤之首,早期诊断困难,晚期患者治疗效果差,分子靶向药物成为近年的研究热点。目前许多靶向药物已经进入临床试验阶段,给卵巢癌特别是术后复发及化疗耐药患者的治疗带来新的希望。本文主要对单克隆抗体,酪氨酸激酶抑制剂等几种药物在卵巢癌的研究进行综述。     

糖代谢与肿瘤化疗靶向药物耐药关系研究进展

恶性肿瘤严重危害人类健康,其发病率和死亡率不断上升。目前临床上治疗恶性肿瘤主要以手术、放化疗和分子靶向治疗为主。近几年,抗肿瘤分子靶向治疗取得了长足进步,与传统的放化疗联合应用获得了更好的疗效。肿瘤多药耐药是临床上化疗和靶向治疗失败的最主要原因之一。产生耐药的肿瘤细胞不仅仅对已使用过的抗肿瘤药物耐药,对未曾使用过的治疗肿瘤和作用机理不同的多种药物也会产生耐药。这种肿瘤的多药耐药,往往是多种耐药蛋白参与及不同机制共同作用的结果。肿瘤细胞能量代谢依赖于糖酵解和氧化磷酸化,而有氧糖酵解是肿瘤细胞能量代谢的重要途径。我们就肿瘤细胞糖酵解调节机制与耐药的关系做简要分析和综述。     

微小RNA在降低HCC分子靶向药物耐药性中的作用

肝细胞癌（HCC）是原发性肝癌的主要组织学类型，大多数患者初诊时即为晚期，生存率较低，一般为5年时间。分子靶向治疗作为晚期HCC患者的重要治疗手段，大部分HCC患者都会因产生不同程度的耐药性而导致肿瘤复发或转移。特异微小RNA通过影响多类信号传导通路参与HCC靶向药耐药的调控，已成为肿瘤及耐药机制研究的热点之一。文章对微小RNA调控HCC耐药性的最新研究进行了综述，以期为解决HCC分子靶向药物耐药性问题找到新的生物标志物和治疗靶点。     

昆虫热激蛋白90的研究进展

热激蛋白90(Heat shock protein 90,Hsp90)是细胞内最为广泛的分子伴侣之一,间接调控细胞内多条与细胞增殖、分化、存活、滞育以及与凋亡相关的信号转导通路。近年来,对Hsp90家族成员在分子水平上的认识不断深入,Hsp90已成为细胞免疫、信号转导以及抗肿瘤研究的前沿课题。昆虫功能基因组的研究正在世界范围内掀起热潮,与昆虫滞育相关热激蛋白的研究也不断深入。对近年来国内外Hsp90的生物学特性、生物学功能及其在昆虫防治中的研究现状及前景进行综述,以期为害虫综合防治的研究提供参考信息。     

辅助伴侣分子Cdc37蛋白的研究进展

细胞分裂周期蛋白Cdc37最初是在芽殖酵母中发现的细胞周期相关蛋白。随后的研究表明Cdc37具有伴侣分子活性,可以特异地募集一系列的蛋白激酶结合到热激蛋白90（Hsp90）上,形成特定的分子伴侣复合体,参与维持蛋白的稳定性和激酶活性。Cdc37参与了细胞内的多项生命活动,在细胞周期、信号转导和基因表达中都起着重要的作用。由于Cdc37在肿瘤组织中特异性地高表达,使其成为肿瘤治疗中一个重要的分子靶点。     

肿瘤靶向治疗在NSCLC中的应用

肺癌已成为21世纪威胁人类健康最主要原因之一,全球每年因非小细胞肺癌(NSCLC)死亡的人数超过100万人.传统的抗肿瘤药物极大改善了NSCLC患者的预后.由于缺乏选择性和很强的细胞毒性,多中心研究表明化疗方案疗效已经达到治疗平台,应致力于研发作用机制不同于化疗的药物.肿瘤靶向治疗通过针对特异性的靶点来杀死和抑制肿瘤细胞,避免了对正常细胞的伤害,已成为当前肿瘤研究的热点,并已在临床肿瘤治疗中取得了一定疗效.随着肿瘤分子生物学与细胞生物学的发展,人们对肺癌癌变、侵袭转移的分子机理以及生物信号传导通路的认识加深,新的靶向治疗药物不断出现.本文就近年靶向治疗技术的进展及分子靶向药物在NSCLC中的应用作一综述.     

Heat shock protein 90: The cancer chaperone

Heat shock protein 90 (Hsp90) is a molecular chaperone required for the stability and function of a number of conditionally activated and/or expressed signalling proteins, as well as multiple mutated, chimeric, and/or over-expressed signalling proteins, that promote cancer cell growth and/or survival. Hsp90 inhibitors are unique in that, although they are directed towards a specific molecular target, they simultaneously inhibit multiple cellular signalling pathways. By inhibiting nodal points in multiple overlapping survival pathways utilized by cancer cells, combination of an Hsp90 inhibitor with standard chemotherapeutic agents may dramatically increase the in vivo efficacy of the standard agent. Hsp90 inhibitors may circumvent the characteristic genetic plasticity that has allowed cancer cells to eventually evade the toxic effects of most molecularly targeted agents. The mechanism-based use of Hsp90 inhibitors, both alone and in combination with other drugs, should be effective toward multiple forms of cancer. Further, because Hsp90 inhibitors also induce Hsf-1-dependent expression of Hsp70, and because certain mutated Hsp90 client proteins are neurotoxic, these drugs display ameliorative properties in several neurodegenerative disease models, suggesting a novel role for Hsp90 inhibitors in treating multiple pathologies involving neurodegeneration.     

Inhibitors of heat shock protein 90 activity: A novel class of tumor radiosensitizers

The 90-kDa heat shock protein (Hsp90) is one of the major chaperones in eukaryotes and catalyzes the maturation and activation of its client proteins. Oncogene products, hormones or growth factor receptors, and key components of signaling pathways are responsible for the malignant growth of tumors or their resistance to chemotherapy and radiotherapy; some of these molecules were identified among the client proteins of Hsp90. Upon the inhibition of Hsp90 chaperone function, such client proteins are inactivated and rapidly degraded, which leads to simultaneous blocking of multiple pathways that are essential for malignant cell proliferation and survival; therefore, pharmacological inhibitors of the Hsp90 chaperone activity could be potentially used in anticancer therapy. Several Hsp90 inhibitors are currently being tested in preclinical or phase I–III clinical trials, either as single agents or in combination with other anticancer drugs or irradiation treatment. In this review, we summarize the data regarding the characterization of Hsp90 inhibitors as efficient radiosensitizers of tumor cells. We also discuss molecular mechanisms and the selectivity of radiosensitization induced by Hsp90 inhibition, as well as a possibility of their application to improve the outcome of radiotherapy.     

Hsp90 inhibitors as novel cancer chemotherapeutic agents

Heat shock protein 90 (Hsp90) is a molecular chaperone whose association is required for the stability and function of multiple mutated, chimeric and over-expressed signaling proteins that promote the growth and/or survival of cancer cells. Hsp90 client proteins include mutated p53, Bcr-Abl, Raf-1, Akt, ErbB2 and hypoxia-inducible factor 1α (HIF-1α). Hsp90 inhibitors, by interacting specifically with a single molecular target, cause the destabilization and eventual degradation of Hsp90 client proteins, and they have shown promising antitumor activity in preclinical model systems. One Hsp90 inhibitor, 17-allylaminogeldanamycin (17AAG), is currently in phase I clinical trial. Because of the chemoprotective activity of several proteins that are Hsp90 clients, the combination of an Hsp90 inhibitor with a standard chemotherapeutic agent could dramatically increase the in vivo efficacy of the therapeutic agent.     

Hsp90 (heat shock protein 90) inhibitor occupancy is a direct determinant of client protein degradation and tumor growth arrest in vivo

Several Hsp90 (heat shock protein 90) inhibitors are currently under clinical evaluation as anticancer agents. However, the correlation between the duration and magnitude of Hsp90 inhibition and the downstream effects on client protein degradation and cancer cell growth inhibition has not been thoroughly investigated. To investigate the relationship between Hsp90 inhibition and cellular effects, we developed a method that measures drug occupancy on Hsp90 after treatment with the Hsp90 inhibitor IPI-504 in living cells and in tumor xenografts. In cells, we find the level of Hsp90 occupancy to be directly correlated with cell growth inhibition. At the molecular level, the relationship between Hsp90 occupancy and Hsp90 client protein degradation was examined for different client proteins. For sensitive Hsp90 clients (e.g. HER2 (human epidermal growth factor receptor 2), client protein levels directly mirror Hsp90 occupancy at all time points after IPI-504 administration. For insensitive client proteins, we find that protein abundance matches Hsp90 occupancy only after prolonged incubation with drug. Additionally, we investigate the correlation between plasma pharmacokinetics (PK), tumor PK, pharmacodynamics (PD) (client protein degradation), tumor growth inhibition, and Hsp90 occupancy in a xenograft model of human cancer. Our results indicate Hsp90 occupancy to be a better predictor of PD than either plasma PK or tumor PK. In the nonsmall cell lung cancer xenograft model studied, a linear correlation between Hsp90 occupancy and tumor growth inhibition was found. This novel binding assay was evaluated both in vitro and in vivo and could be used as a pharmacodynamic readout in the clinic.     

Lead generation of heat shock protein 90 inhibitors by a combination of fragment-based approach, virtual screening, and structure-based drug design

Heat shock protein 90 (Hsp90) is a molecular chaperone which regulates maturation and stabilization of its substrate proteins, known as client proteins. Many client proteins of Hsp90 are involved in tumor progression and survival and therefore Hsp90 can be a good target for developing anticancer drugs. With the aim of efficiently identifying a new class of orally available inhibitors of the ATP binding site of this protein, we conducted fragment screening and virtual screening in parallel against Hsp90. This approach quickly identified 2-aminotriazine and 2-aminopyrimidine derivatives as specific ligands to Hsp90 with high ligand efficiency. In silico evaluation of the 3D X-ray Hsp90 complex structures of the identified hits allowed us to promptly design CH5015765, which showed high affinity for Hsp90 and antitumor activity in human cancer xenograft mouse models.     

Therapeutic and diagnostic implications of Hsp90 activation

The molecular chaperone heat-shock protein 90 (Hsp90) is involved in the stabilization and conformational maturation of many signaling proteins that are deregulated in cancers. Hsp90 inhibition results in the proteasomal degradation of these client proteins and leads to potent antitumor activity. The Hsp90 inhibitor 17-allylaminogeldanamycin (17-AAG) is presently in clinical trials. Recent work has identified the role of Hsp90 in multiple signal transduction pathways and revealed that the molecular mechanism of tumor selectivity by Hsp90 inhibitors is the result of an activated, high-affinity conformation of Hsp90 in tumors. This review discusses these recent advances in the understanding of tumor Hsp90 for the treatment and diagnosis of cancer. In addition, the role of Hsp90 in non-oncological diseases will also be discussed.     

Heat shock protein 90 indirectly regulates ERK activity by affecting Raf protein metabolism

Extracellular signal-regulated protein kinase (ERK) has been implicated in the pathogenesis of several nerve system diseases. As more and more kinases have been discovered to be the client proteins of the molecular chaperone Hsp90, the use of Hsp90 inhibitors to reduce abnormal kinase activity is a new treatment strategy for nerve system diseases. This study investigated the regulation of the ERK pathway by Hsp90. We showed that Hsp90 inhibitors reduce ERK phosphorylation without affecting the total ERK protein level. Further investigation showed that Raf, the UPstream kinase in the Ras-Raf-MEK-ERK pathway, forms a complex with Hsp90 and Hsp70. Treating cells with Hsp90 inhibitors facilitates Raf degradation,thereby down-regulating the activity of ERK.     

Surface charge and hydrophobicity determine ErbB2 binding to the Hsp90 chaperone complex

The molecular chaperone Hsp90 modulates the function of specific cell signaling proteins. Although targeting Hsp90 with the antibiotic inhibitor geldanamycin (GA) may be a promising approach for cancer treatment, little is known about the determinants of Hsp90 interaction with its client proteins. Here we identify a loop within the N lobe of the kinase domain of ErbB2 that determines Hsp90 binding. The amino acid sequence of the loop determines the electrostatic and hydrophobic character of the protein's surface, which in turn govern interaction with Hsp90. A point mutation within the loop that alters ErbB2 surface properties disrupts Hsp90 association and confers GA resistance. Notably, the immature ErbB2 point mutant remains sensitive to GA, suggesting that mature and nascent client kinases may use distinct motifs to interact with the Hsp90 chaperone complex.     

Inhibition of heat shock protein (Hsp) 27 potentiates the suppressive effect of Hsp90 inhibitors in targeting breast cancer stem-like cells

Heat shock protein (Hsp) 90 is an ATP-dependent chaperone and its expression has been reported to be associated with poor prognosis of breast cancer. Cancer stem cells (CSCs) are particular subtypes of cells in cancer which have been demonstrated to be important to tumor initiation, drug resistance and metastasis. In breast cancer, breast CSCs (BCSCs) are identified as CD24-CD44 + cells or cells with high intracellular aldehyde dehydrogenase activity (ALDH+). Although the clinical trials of Hsp90 inhibitors in breast cancer therapy are ongoing, the BCSC targeting effect of them remains unclear. In the present study, we discovered that the expression of Hsp90α was increased in ALDH + human breast cancer cells. Geldanamycin (GA), a Hsp90 inhibitor, could suppress ALDH + breast cancer cells in a dose dependent manner. We are interesting in the insufficiently inhibitory effect of low dose GA treatment. It was correlated with the upregulation of Hsp27 and Hsp70. By co-treatment with HSP inhibitors, quercetin or KNK437 potentiated BCSCs, which determined with ALDH+ population or mammosphere cells, toward GA inhibition, as well as anti-proliferation and anti-migration effects of GA. With siRNA mediated gene silencing, we found that knockdown of Hsp27 could mimic the effect of HSP inhibitors to potentiate the BCSC targeting effect of GA. In conclusion, combination of HSP inhibitors with Hsp90 inhibitors could serve as a potential solution to prevent the drug resistance and avoid the toxicity of high dose of Hsp90 inhibitors in clinical application. Furthermore, Hsp27 may play a role in chemoresistant character of BCSCs.     

Hsp90 Inhibitors Exhibit Resistance-Free Antiviral Activity against Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is a major cause of respiratory illness in young children, leading to significant morbidity and mortality worldwide. Despite its medical importance, no vaccine or effective therapeutic interventions are currently available. Therefore, there is a pressing need to identify novel antiviral drugs to combat RSV infections. Hsp90, a cellular protein-folding factor, has been shown to play an important role in the replication of numerous viruses. We here demonstrate that RSV requires Hsp90 for replication. Mechanistic studies reveal that inhibition of Hsp90 during RSV infection leads to the degradation of a viral protein similar in size to the RSV L protein, the viral RNA-dependent RNA polymerase, implicating it as an Hsp90 client protein. Accordingly, Hsp90 inhibitors exhibit antiviral activity against laboratory and clinical isolates of RSV in both immortalized as well as primary differentiated airway epithelial cells. Interestingly, we find a high barrier to the emergence of drug resistance to Hsp90 inhibitors, as extensive growth of RSV under conditions of Hsp90 inhibition did not yield mutants with reduced sensitivity to these drugs. Our results suggest that Hsp90 inhibitors may present attractive antiviral therapeutics for treatment of RSV infections and highlight the potential of chaperone inhibitors as antivirals exhibiting high barriers to development of drug resistance.