细胞周期蛋白依赖激酶抑制剂:一类全新的抗肿瘤药物

细胞周期蛋白依赖激酶(cyclin-dependent kinase,CDKs)是调控细胞周期的一个蛋白家庭[1],其成员有CDK1～CDK9,共9种,其中有CDK1～CDK7与其相应的调节亚基即细胞周期蛋白(cyclin)组成的复合物可推动细胞跨越细胞周期各时相转换的限制点[2],使细胞完成由G1→S→G2→M各期的转换过程,对细胞分裂增殖的调控处于核心地位.因此,作为一个新的治疗靶点,CDKs抑制剂的研究是目前抗肿瘤药物研究与开发的热点之一[3].笔者现将这类药物作如下综述.     

临床试验阶段的CDK抑制剂的研究进展

细胞周期（cell cycle）是指细胞从上一次有丝分裂结束到下一次有丝分裂完成的整个过程。一个完整的细胞周期包括G1期、S期、G2期和M期。细胞周期的有序运行主要依赖于cyclin／细胞周期蛋白依赖性激酶（CDK）复合物的表达。细胞周期蛋白（cyclin）、CDK的异常表达，CDK抑制蛋白的缺失都会导致细胞周期紊乱，细胞增殖失控，发生癌变。近年来的研究证实，Rb蛋白家族是细胞周期的“开关”，Rb蛋白被细胞周期蛋白依赖性激酶（CDKs）磷酸化后，细胞才能分化增殖。     

细胞周期素依赖蛋白激酶9抑制剂的抗肿瘤研究进展

细胞周期素依赖蛋白激酶(CDKs)是一类丝氨酸/苏氨酸激酶,它不仅在细胞周期调节过程中发挥着至关重要的作用,而且是细胞转录过程中的重要调节因子。CDK9可以磷酸化RNA聚合酶Ⅱ的C-末端以及调控其他转录调节因子,从而促进转录的延长。目前已有多个用于肿瘤治疗的CDK9抑制剂进入临床试验阶段。本文介绍了CDK9的功能、结构以及CDK9在转录过程中的作用,重点对目前报道的在肿瘤治疗领域的CDK9小分子抑制剂的研究进行综述。     

基于PROTAC技术的靶向CDK9小分子降解剂的研究进展

CDKs蛋白是一种细胞周期蛋白依赖性激酶,它们在控制细胞分裂及转录阶段发挥着重要的作用。其中, CDK9作为一种负责细胞转录延伸阶段的关键调控因子,驱动着各种恶性肿瘤细胞的发生,被认为是抗肿瘤药物研发领域的重要靶标。然而,由于CDK家族蛋白结构的高度保守性及相似性,导致传统小分子CDK9抑制剂的选择性较差,存在严重的不良反应而限制了其临床应用。鉴于此,当前迫切需要一种全新策略来研究CDK9靶点。蛋白降解靶向嵌合体(PROTAC)技术是一种新兴的药物研发策略,通过靶蛋白与泛素连接酶的间接性链接,特异性地识别靶蛋白并通过降解系统来消除目标蛋白。本文对CDK9蛋白的结构功能、与临床疾病预后不良产生的关系及明星小分子抑制剂进行简要概述,重点讨论了近几年基于PROTAC技术靶向降解CDK9蛋白的最新研究进展,并对该靶点蛋白在这一新型技术领域内的发展前景进行了总结和展望,旨在为该方向的抗肿瘤药物研发提供参考。     

细胞周期蛋白激酶抑制剂研究现状

目前普遍观点认为,肿瘤产生的本质是细胞增殖的调节失控,而细胞的增殖要通过细胞周期来调控。细胞周期调控激酶复合物[cyclin dependent kinase（CDK）/Cyclin]活性的异常是导致细胞周期失控的根本原因。抑制CDK/Cyclin激酶的活性成为有效治疗肿瘤的策略之一。因此,针对CDK/Cyclin激酶抑制剂的研究是当前抗肿瘤药物开发的热点之一。本文对近年来CDK/cyclin抑制剂的种类及目前其在临床应用中出现的问题进行概述。     

扫描新的化学分子[英]

具有抗肿瘤活性的细胞周期依赖性激酶和Aurora激酶双重抑制剂Aurora激酶可控制染色体运动和组装，确保染色体分离进入子细胞的过程中有丝分裂纺锤体形成，故作为极具潜力的抗肿瘤药物靶标引起广泛关注。因此，小分子的CDK和（或）Aurora激酶抑制剂可能有效地抑制肿瘤细胞增殖，对多种类型的肿瘤具有治疗作用。     

细胞周期蛋白依赖激酶小分子抑制剂的研究进展

细胞周期和肿瘤的关系是近年来生命科学研究的热门课题之一。细胞周期调控异常与细胞癌变密切相关，在90％以上的人肿瘤中，尤其是胶质瘤和软组织肉瘤中细胞周期蛋白依赖激酶（CDKs）都有过度表达。因此，有人认为肿瘤是一种细胞周期疾病（cellcycledisease）。近年来细胞周期调控最具突破性的进展，确定了细胞周期进程的分子机制，其核心机制为CDKs的活性表达与调控。本文将就细胞周期蛋白依赖性激酶及其抑制剂的研究进展作一综述。     

细胞周期依赖蛋白激酶小分子抑制剂的研究进展

研究发现，几乎所有的肿瘤都与细胞周期调控机制紊乱所导致的细胞生长失控、分化受阻、凋亡异常有关．而细胞周期蛋白依赖激酶（cyclin-dependent kinases。CDKs）的过度活化则是重要原因。随着近年来对CDKs作用机制研究的逐渐深入．出现了种类繁多的小分子抑制剂。本文针对近年来CDKs小分子抑制荆及其研究进展作一综述。     

细胞周期蛋白依赖性激酶抑制剂

目的　系统介绍细胞周期蛋白依赖性激酶(CDK)抑制剂的抗肿瘤作用。方法　对近几年国外有关CDK抑制剂的发现、构效研究及临床试验等文献进行检索和综述。结果　olomoucine,roscovitine等三取代嘌呤类化合物,flavopiridol及butyrolac tone三类化合物具有明显的CDK抑制活性,对多种人类肿瘤均有疗效,且不良反应小。结论　细胞周期蛋白依赖性激酶(CDK)抑制剂有望成为新一代抗肿瘤药     

4-氨基-2-三氟甲基苯基维甲酸酯诱导K562细胞分化的作用及细胞周期阻滞的作用机制

目的：本研究探讨新型维甲酸衍生物4-氨基-2-三氟甲基苯基维甲酸酯（4-amino-2-trifluoromethyl—phenylretinate,ATPR）对K562细胞株的抑制增殖的和诱导分化活性并对其发生的细胞周期G1期阻滞的机制进行研究。方法：ATPR作用于K562细胞3d后,通过MTT法检测细胞的增殖,NBT还原实验法分析细胞的分化指标,FCM检测分析细胞周期和细胞表面分化抗原CD45、CD73、CD117变化。RT—PCR法检测细胞周期蛋白cyclinE、cyclinD1,细胞周期蛋白依赖性激酶CDK2、CDK4、CDK6,周期蛋白抑制蛋白／激酶抑制蛋白（CIP／KIP）P21（cipl）、P27（kipl）、P57（kip2）mRNA的变化情况。WesternBlot法检测cyclinDl和CDK4蛋白表达的改变。结果：ATPR呈浓度依赖性抑制K562细胞增殖的作用。     

Dual action of cyclin-dependent kinase inhibitors: induction of cell cycle arrest and apoptosis. A comparison of the effects exerted by roscovitine and cisplatin

Cyclin-dependent kinases (CDKs) have recently raised considerable interest in view of their key role in the regulation of the cell cycle progression. In proliferating cells, distinct CDKs associated with specific cyclins coordinate in an orchestrated way the appropriate transition between different phases of the cell cycle. Mutations and/or aberrant expression of distinct CDKs and their regulatory components lead to uncontrolled proliferation and finally to carcinogenesis. However, in post-mitotic neurons, all CDKs with the exception of CDK5 are silent. CDK5, a proline-directed serine/threonine kinase exhibiting a close structural homology to the mitotic CDKs, binds to p35, the neuron-specific regulatory subunit of CDK5. CDK5 is very abundant in mature neurons and seems to regulate neurotransmitter release through phosphorylation and down-regulation of calcium channel activity. Therefore, the inhibition of CDKs in neurons after oxidative stress and in neurodegenerative disorders has a protective action. Selective CDKs inhibitors were developed as promising drugs for cancer therapy due to their ability to arrest cell cycle progression. The aim of this study was to compare the anti-proliferative effect of roscovitine (ROSC), a potent CDKs inhibitor, with that of cisplatin (CP) on human breast cancer MCF-7 cells. ROSC exerted stronger inhibitory effect on proliferation and cell cycle progression of MCF-7 than CP. Accumulation of G(2)/M arrested cells starting 6 h after onset of ROSC treatment coincided with a strong up-regulation of the p53. Reconstitution with caspase-3 sensitized MCF-7 cells to CP action. It implicates that ROSC inhibits more selectively and efficaciously the proliferation of human breast carcinoma cells.     

Cyclin-dependent protein kinases as therapeutic drug targets for antimalarial drug development

Cyclin-dependent protein kinases (CDKs) have been attractive drug targets for the development of anticancer therapies due to their direct and crucial role in the regulation of cellular proliferation. Following this trend, CDKs have been pursued as potential drug targets for several other diseases. Structure-based drug design programmes have focused on the plasmodial CDKs to develop new candidate antimalarial compounds. This review discusses the most recent advances relating to three Plasmodium falciparum CDKs (PfPK5, PfPK6 and Pfmrk) as they are developed as antimalarial drug targets. CDKs are highly conserved, and focus must be placed upon the amino acid differences between human and plasmodial CDKs in order to develop specific inhibitors. Comparisons of the active sites of human and parasite CDKs reveal sequence and potential structural variations. Using sequence analysis, molecular modelling and in vitro drug screening, it is possible to identify and develop inhibitors that specifically target the plasmodial CDKs. These efforts are aimed at identifying new classes of CDK inhibitors that may be exploited for antimalarial drug development.     

Inhibiting cyclin-dependent kinase/cyclin activity for the treatment of cancer and cardiovascular disease

Excessive cell proliferation contributes to the pathobiology of human diseases with a high health and socio-economic impact, including cancer and vascular occlusive diseases (e. g., atherosclerosis, in-stent restenosis, transplant vasculopathy, and vessel bypass graft failure). Recent advances in the understanding of the molecular networks governing the hyperplastic growth of tumors and vascular obstructive neointimal lesions have provided new perspectives for preventive and therapeutic strategies against these disorders. Mammalian cell proliferation requires the activation of several cyclin-dependent protein kinases (CDKs). Postranslational activation of CDKs is a complex process that involves their association with regulatory subunits called cyclins. The activity of CDK/cyclin holoenzymes is negatively regulated through their interaction with members of the CDK family of inhibitory proteins (CKIs). Moreover, over fifty low molecular weight pharmacological CDK inhibitors that target the ATP-binding pocket of the catalytic site of CDKs have been identified. In this review, we will discuss the use of pharmacological and gene therapy strategies against CDK/cyclins in animal models and clinical trials of cancer and cardiovascular disease.     

Inhibition of cellular proliferation by drug targeting of cyclin-dependent kinases

Abnormal cellular proliferation is associated with the pathology of several diseases, including cancer, atherosclerosis and restenosis post-angioplasty. Therefore, antiproliferative therapies may be a suitable approach to treat these disorders. Candidate targets for such strategies include specific components of the cell cycle machinery. Progression through the cell cycle in mammalian cells requires the activation of several cyclin-dependent protein kinases (CDKs) through their association with regulatory subunits called cyclins. Active CDK/cyclin holoenzymes phosphorylate cellular proteins including the retinoblastoma susceptibility gene product (pRb) and the related pocket proteins p107 and p130. Several compounds have been described that directly or indirectly inhibit the activity of CDKs, which results in a suppression of cell growth. In this review, we will discuss the use of drugs targeting CDKs and their therapeutic application in animal models and clinical trials.     

抗肿瘤细胞周期蛋白依赖性激酶抑制剂的研究进展

细胞周期是细胞生命活动的基本特征。一个完整的细胞周期受多种蛋白酶的调控,调控失调会导致细胞过度增殖,从而引发肿瘤。以细胞周期蛋白依赖性激酶（cyclin．dependent kinases,CDKs）为靶点的药物可以阻断细胞周期,控制细胞增殖,从而达到抗肿瘤的目的。现简单介绍细胞周期依赖性蛋白激酶、细胞周期蛋白、细胞周期调控机制及其与肿瘤的关系,对近年来不同结构类型的细胞周期蛋白激酶抑制剂进行综述,并初步分析其发展趋势。     

Inhibitors of cyclin dependent kinases: useful targets for cancer treatment

Cancer drug discovery is one of the most rapidly changing areas of pharmaceutical research. Uncontrolled proliferation is a hallmark of cancer cells. Over the past two decades, it has become increasingly clear that in many human cancers, hyperactivity of Cyclin Dependent Kinases (CDKs) is one of the mechanisms underlying the physiological hyper-proliferation. CDKs are serine/threonine protein kinases, which play an important role in cell-cycle regulation. Their sequential activation ensures, the correct timing and ordering of events required for cell cycle progression. Therefore, inhibition of CDKs, through the insertion of small molecules into its ATP binding pocket has emerged as a potential therapy method for cancers. Consequently, a number of small molecules with CDK inhibitory properties have been developed. Many of these have been evaluated as potent inhibitors and some are currently in clinical-trials for various types of cancer. This review reports various CDK inhibitors, natural as well as small molecules, along with their reported activities for various CDKs. It will highlight the potential for the development of novel anti-cancer molecules.     

Purvalanol A, inhibitor of cyclin-dependent kinases attenuates proliferation of cells in the dentate gyrus of the adult rat hippocampus

Several recent findings indicate that intensity of neurogenesis in adult brain might be regulated by enzymes involved in the cell cycle. Therefore, in the present study, we investigated whether the inhibition of cyclin-dependent kinases (CDKs) evoked by intraventricular administration of purvalanol A may influence the proliferation of cells in the dentate gyrus (DG) of the rat hippocampus. Purvalanol A, a selective inhibitor of CDKs, was injected into the brain lateral ventricle at concentrations of 4 nmol/3 microl or 40 nmol/3 microl. The number of proliferating cells was determined by analysis of nuclear incorporation of BrdU (100 mg/kg, i.p.). BrdU was given at two times points (0.5 h and 2.5 h) after vehicle or purvalanol A injection. It was found that purvalanol A given 0.5 h before BrdU injection did not cause any significant changes in the number of BrdU-positive nuclei in the DG. However, a higher dose of purvalanol A i.e. 40 nmol/3 microl given 2.5 h before BrdU administration significantly decreased the number of BrdU-positive nuclei in the DG of the hippocampus (by approximately 35%). In contrast, a lower dose of the CDKs inhibitor (4 nmol/3 microl) given at the same time point did not affect the number of BrdU-positive cells in the DG. It appears that purvalanol A inhibits the hippocampal proliferation in concentration- and time-dependent manner. Moreover, the present data indicate that CDKs are involved in generation of new cells in the adult rat hippocampus.     

Recent advances and new directions in the discovery and development of cyclin-dependent kinase inhibitors

The eukaryotic cell division cycle is coordinated by cyclin-dependent protein kinases (CDKs) and cyclin subunits specific for the different phases of the cycle. These complexes phosphorylate target substrates, including the retinoblastoma susceptibility gene product (pRb) and related proteins. Cellular neoplastic transformations are accompanied by loss of regulation of cell cycle checkpoints, frequently through aberrant expression of CDKs and cyclins, as well as loss or mutation of their negative regulators. Consequently, one strategy in the development of mechanism-based anticancer therapeutics has been to halt malignant cellular proliferation through inhibition of the enzymatic activity of CDKs. The development of inhibitors selective for the ATP binding sites of particular protein kinases is a comparatively recent medicinal chemistry endeavor. Advances relevant to CDK inhibition are reviewed critically and alternative approaches to CDK inhibition, as well as applications of CDK inhibitors to therapeutic areas other than oncology, are also discussed.     

Cyclin-dependent kinases as therapeutic targets for HIV-1 infection

Introduction: A number of cyclin-dependent kinases (CDKs) mediate key steps in the HIV-1 replication cycle and therefore have potential to serve as therapeutic targets for HIV-1 infection, especially in HIV-1 cure strategies. Current HIV-1 cure strategies involve the development of small molecules that are able to activate HIV-1 from latent infection, thereby allowing the immune system to recognize and clear infected cells.

Areas covered: The role of seven CDK family members in the HIV-1 replication cycle is reviewed, with a focus on CDK9, as the mechanism whereby the viral Tat protein utilizes CDK9 to enhance viral replication is known in considerable detail.

Expert opinion: Given the essential roles of CDKs in cellular proliferation and gene expression, small molecules that inhibit CDKs are unlikely to be feasible therapeutics for HIV-1 infection. However, small molecules that activate CDK9 and other select CDKs such as CDK11 have potential to reactivate latent HIV-1 and contribute to a functional cure of infection.