MiR-132抑制肿瘤转移

肿瘤转移是造成癌症难以根治的重要原因之一.近年来越来越多的研究发现,miRNA在肿瘤转移过程中发挥了直接或间接的作用.本研究的目标是找到一种特异性的肿瘤转移相关miRNA,能够作为抑制肿瘤转移的潜在靶标.miR-132是一类与炎症、血管生长、中枢神经系统相关的miRNA,至今还没有研究证明其与肿瘤转移相关.为了验证miR-132与肿瘤迁移的相关性,本研究将miR-132转染入高迁移乳腺癌细胞系MDA-MB-231细胞中,检测细胞迁移率的变化.实验发现miR-132能够抑制MDA-MB-231细胞的迁移.为了进一步揭示miR-132抑制细胞迁移的可能机制,本研究通过生物信息学手段寻找并鉴定了3种可能与肿瘤转移相关的miR-132的靶基因,它们分别是CHIP(STUB1)、G3BP1、G3BP2.分别比对MCF7与MDA-MB-231细胞,及转染miR-132和对照组MDA-MB-231细胞中以上3种基因的表达差异,我们发现G3BP1、G3BP2可能参与miR-132对肿瘤转移的调控.本研究首次报道miR-132与肿瘤转移的关系,并揭示了miR-132调节肿瘤转移的可能机制,说明了miR-132具有作为特异性抑制肿瘤转移靶标的潜力,为抑制肿瘤转移提供一个新的靶点.     

沉默DEPDC1抑制鼻咽癌细胞HNE-1和CNE-1侵袭迁移

DEPDC1(DEP domain containing 1)是一个新的肿瘤相关基因,在多种恶性肿瘤的发生发展进程中起着重要作用。我们前期工作中在鼻咽癌细胞内沉默了DEPDC1的表达,发现抑制细胞增殖并诱发细胞凋亡。本研究旨在探讨沉默DEPDC1表达后,对鼻咽癌细胞HNE-1和CNE-1侵袭迁移能力的影响及其分子机制。结果显示,siRNA介导DEPDC1表达沉默后,细胞侧向运动能力、侵袭及迁移能力显著降低。qRT-PCR及Western印迹检测发现DEPDC1沉默导致EMT上游关键转录因子Twist1及间质细胞标志分子Vimentin表达显著下调。这些研究表明,鼻咽癌细胞中DEPDC1通过调节Twist1等EMT关键分子的表达在细胞侵袭转移过程中起关键作用。推测DEPDC1在鼻咽癌中高表达可能对于促进其侵袭转移具有重要作用,进而促进肿瘤发生发展,但具体分子机制仍有待更深入研究。     

Cell Rep:阻断自噬将癌细胞牢牢粘在原地

正来自美国芝加哥大学的研究人员最近发现抑制细胞的自噬过程能够有效阻断肿瘤细胞迁移和肿瘤模型中的乳腺癌转移。这项研究表明自噬过程在肿瘤转移过程中发挥非常重要的作用,同时详细阐述了自噬促进细胞迁移的分子机制。相关研究结果发表在国际学术期刊Cell Reports上。     

miR-21在非小细胞肺癌中的研究进展

肺癌是我国最常见的恶性肿瘤,发病率高且预后差。mi R-21可通过转录后调控机制调节多种与细胞增殖、血管生成和侵袭迁移相关的肿瘤抑制因子的表达,在肿瘤的发生发展及转移中发挥重要作用。mi R-21在非小细胞肺癌中高表达,与非小细胞肺癌细胞增殖、血管生成、侵袭和转移密切相关,是一个潜在的肺癌诊断与转移的分子靶标。     

DKK-1通过上调nm23表达抑制乳腺癌细胞迁移

Dickkopf-1(DKK-1)作为Wnt/β-连环蛋白(Wnt/β-catenin)经典信号传导通路的拮抗剂而受到关注.为了进一步阐明DKK-1在乳腺癌细胞迁移中的作用及其分子机制,应用我们建立的乳腺癌细胞MCF-7高转移倾向亚克隆LM-MCF-7细胞株,比较了DKK-1在不同转移能力的乳腺癌细胞株中表达水平及其与细胞迁移能力的关系.结果显示,DKK-1在LM-MCF-7细胞中表达明显下调;"伤口愈合"实验结果表明,在MCF-7细胞中,RNA干扰DKK-1可导致细胞迁移能力增强;相反,在LM-MCF-7细胞中过表达DKK-1则可抑制细胞的迁移.进一步研究结果显示,DKK-1为肿瘤转移抑制因子nm23的上游激活因子.因此,我们的研究结果表明,DKK-1表达水平下调导致nm23表达水平下调,解除了对乳腺癌细胞迁移的抑制作用,是LM-MCF-7乳腺癌细胞具有高迁移能力的原因之一;反之,与LM-MCF-7相比,DKK-1在MCF-7细胞中高表达,其通过上调nm23可抑制乳腺癌细胞迁移.这一发现对进一步揭示乳腺癌细胞转移的分子机制具有的重要意义.     

乳腺癌细胞迁移的调节与转移

细胞迁移是乳腺癌侵袭和转移中的关键步骤之一.癌细胞在迁移过程中主要受到Rho GTPases的调节,发生肌动蛋白骨架重组,获得定向迁移的能力;高迁移能力的癌细胞通过与胞外基质成分相互作用,为迁移创造合适的微环境;最后迁移的癌细胞在靶器官的趋化作用下在特定部位驻足生长,这些环节共同作用导致乳腺癌转移.研究细胞迁移复杂的分子机制将为控制乳腺癌转移提供新的策略.     

黄芩甙对人肝癌BEL-7402细胞增殖和侵袭转移的影响及机制

目的探讨黄芩甙对人肝癌BEL-7402细胞系增殖、侵袭转移的影响及其机制。方法应用细胞培养技术培养人肝癌BEL-7402细胞,MTT实验、软琼脂克隆形成实验检测黄芩甙对肝癌细胞增殖的影响。通过Boyaen小室模型测定其侵袭力,细胞迁移实验测定细胞运动能力,同时观察细胞形态。流式细胞术测定肝癌细胞MMP2、TIMP2表达,免疫组化测定VEGF表达。结果黄芩甙能明显抑制肝癌细胞增殖,细胞侵袭力及运动能力明显下降,且呈量效关系（P〈0．05）。形态学观察发现,黄芩甙处理组细胞形态较圆,伪足数目较少;MMP2阳性表达细胞减少,TIMP2阳性表达细胞增多,MMP2／TIMP2比值下降;VEGF表达减少。结论黄芩甙能抑制肝癌BEL-7402增殖、侵袭与转移,其机制可能与直接抑制细胞迁移运动,抑制细胞基质溶解相关基因蛋白MMP2表达,促进TIMP2表达;VEGF表达减少有关。     

肿瘤转移中E-钙粘蛋白的调控

E-钙粘蛋白是参与细胞间粘附连接的主要分子,发挥着维持细胞极性和组织结构完整性的功能.肿瘤组织中E-钙粘蛋白介导的细胞间粘附力减弱,使细胞获得浸润性和游走迁移能力.在细胞迁移到新的位置后,E-钙粘蛋白重新表达,有利于肿瘤细胞在继发部位生长增殖,形成新的病灶.E-钙粘蛋白功能调控在肿瘤转移中的作用主要涉及到以下几种机制,编码基因修饰,基因转录抑制及microRNA调节.其中microRNA通过影响E-钙粘蛋白的转录或表达在肿瘤转移过程发挥了重要作用,为肿瘤转移的临床诊断和靶向治疗开辟了新的思路.本文主要就肿瘤转移过程中E-钙粘蛋白的表达变化以及相应调控机制做一综述.     

死亡相关蛋白激酶的功能及其与肿瘤转移的关系

死亡相关蛋白激酶（DAPK）可通过p53途径诱导细胞的凋亡,并与细胞自噬过程相关,可抑制整合素活化抑制细胞黏附．以及影响细胞的极化影响细胞的迁移,是一个与肿瘤的发生、转移密切相关的蛋白质。该文介绍近年来有关DAPK与肿瘤发病及其与肿瘤转移的关系。     

钙通道蛋白Orai1在骨肉瘤细胞转移中的作用研究

目的:骨肉瘤是一种常见的恶性骨肿瘤,恶性程度高,往往在早期就会发生远隔器官的转移,从而导致骨肉瘤的预后非常差。Orai1是一类定位于细胞膜,介导钙离子内流的受体依赖性钙通道蛋白。大量研究发现钙通道蛋白Orai1过表达于多种肿瘤细胞,并对维持肿瘤细胞粘附、侵袭、迁移等恶性表型有非常重要的作用。然而,钙通道蛋白Orai1是否参与了骨肉瘤的转移过程,目前未见相关报道。本研究的目的是探究钙通道蛋白Orai1是否在骨肉瘤转移过程中的发挥作用。方法:利用合成的靶向Orai1的小干扰RNA(Orai1 si RNA)片段,转染至人骨肉瘤细胞系Saos-2细胞。在Saos-2细胞中抑制Orai1的表达。采用细胞黏附实验、细胞划痕实验和细胞Transwell实验检测骨肉瘤细胞的黏附、迁移及侵袭等肿瘤细胞转移能力;Western-blot实验检测Saos-2细胞的中黏着斑激酶(FAK)和桩蛋白(Paxillin)的表达水平和磷酸化水平。结果:靶向Orai1 si RNA瞬时转染至骨肉瘤细胞系Saos-2细胞后,Saos-2细胞中Orai1蛋白表达水平和m RNA转录水平均显著下降。并且,在Saos-2细胞中抑制Orai1表达后,Saos-2细胞的黏附能力、迁移能力、及侵袭能力均显著下降。进一步研究发现,在Saos-2细胞中抑制Orai1表达后,Saos-2细胞的FAK和Paxillin磷酸化水平明显下降。结论:Orai1可以促进骨肉瘤细胞的黏附、迁移和侵袭,增加黏着斑的形成,从而促进骨肉瘤的转移。因此,深入研究钙通道蛋白Orai1调控骨肉瘤转移的分子机制,可为骨肉瘤转移的治疗提供新的新方向和新策略。     

Integrin and Cadherin Synergy Regulates Contact Inhibition of Migration and Motile Activity

Integrin receptors play a central role in cell migration through their roles as adhesive receptors for both other cells and extracellular matrix components. In this study, we demonstrate that integrin and cadherin receptors coordinately regulate contact-mediated inhibition of cell migration. In addition to promoting proliferation (Sastry, S., M. Lakonishok, D. Thomas, J. Muschler, and A. Horwitz. 1996. J. Cell Biol. 133:169–184), ectopic expression of the α5 integrin in cultures of primary quail myoblasts promotes a striking contact-mediated inhibition of cell migration. Myoblasts ectopically expressing α5 integrin (α5 myoblasts) move normally when not in contact, but upon contact, they show inhibition of migration and motile activity (i.e., extension and retraction of membrane protrusions). As a consequence, these cells tend to grow in aggregates and do not migrate to close a wound. This phenotype is also seen with ectopic expression of β1 integrin, paxillin, or activated FAK (CD2 FAK) and therefore appears to result from enhanced integrin-mediated signaling. The contact inhibition observed in the α5 myoblasts is mediated by N-cadherin, whose expression is upregulated more than fivefold. Perturbation studies using low calcium conditions, antibody inhibition, and ectopic expression of wild-type and mutant N-cadherins all implicate N-cadherin in the contact inhibition of migration. Ectopic expression of N-cadherin also produces cells that show inhibited migration upon contact; however, they do not show suppressed motile activity, suggesting that integrins and cadherins coordinately regulate motile activity. These observations have potential importance to normal and pathologic processes during embryonic development and tumor metastasis.     

Competition amongst Eph receptors regulates contact inhibition of locomotion and invasiveness in prostate cancer cells

Metastatic cancer cells typically fail to halt migration on contact with non-cancer cells. This invasiveness is in contrast to normal mesenchymal cells that retract on contact with another cell. Why cancer cells are defective in contact inhibition of locomotion is not understood. Here, we analyse the dynamics of prostate cancer cell lines co-cultured with fibroblasts, and demonstrate that a combinatorial code of Eph receptor activation dictates whether cell migration will be contact inhibited. The unimpeded migration of metastatic PC-3 cells towards fibroblasts is dependent on activation of EphB3 and EphB4 by ephrin-B2, which we show activates Cdc42 and cell migration. Knockdown of EphB3 and EphB4 restores contact inhibition of locomotion to PC-3 cells. Conversely, homotypic collisions between two cancer cells results in contact inhibition of locomotion, mediated by EphA-Rho-Rho kinase (ROCK) signalling. Thus, the migration of cancer cells can switch from restrained to invasive, depending on the Eph-receptor profile of the cancer cell and the reciprocal ephrin ligands expressed by neighbouring cells.     

Depletion of GRIM-19 accelerates hepatocellular carcinoma invasion via inducing EMT and loss of contact inhibition

Genes associated with retinoid-interferon-induced mortality 19 (GRIM-19) was identified as a tumor suppressor protein associated with apoptosis and growth inhibition. Here, we report that the expression levels of GRIM-19 are significantly attenuated in hepatocellular carcinoma (HCC) patients with deteriorating differentiation states, hepatic capsule invasion and microvascular invasion, suggesting the potential role of GRIM-19 not only at the origin but also in the invasive progression of HCCs. To dissect the possible mechanisms by which GRIM-19 regulates tumor cell invasion, we established the hepatic HL-7702 and HCC Huh-7 cell lines stably depleted of GRIM-19. Results show that downregulation of GRIM-19 induces a morphological transformation resembling epithelial-mesenchymal transition (EMT) as well as aberrant expression of epithelial and mesenchymal molecular markers. Additionally, these cells lose contact inhibition, a phenomenon of cessation of cell migration in contact with neighboring cells, as assessed by cell imaging, growth curve and S-phase transition in confluent conditions. CONCLUSION: Our observations demonstrate a novel mechanistic insight into a critical role of GRIM-19 in HCC invasive potential.     

Src Induces Podoplanin Expression to Promote Cell Migration

Nontransformed cells can force tumor cells to assume a normal morphology and phenotype by the process of contact normalization. Transformed cells must escape this process to become invasive and malignant. However, mechanisms underlying contact normalization have not been elucidated. Here, we have identified genes that are affected by contact normalization of Src-transformed cells. Tumor cells must migrate to become invasive and malignant. Src must phosphorylate the adaptor protein Cas (Crk-associated substrate) to promote tumor cell motility. We report here that Src utilizes Cas to induce podoplanin (Pdpn) expression to promote tumor cell migration. Pdpn is a membrane-bound extracellular glycoprotein that associates with endogenous ligands to promote tumor cell migration leading to cancer invasion and metastasis. In fact, Pdpn expression accounted for a major part of the increased migration seen in Src-transformed cells. Moreover, nontransformed cells suppressed Pdpn expression in adjacent Src-transformed cells. Of >39,000 genes, Pdpn was one of only 23 genes found to be induced by transforming Src activity and suppressed by contact normalization of Src-transformed cells. In addition, we found 16 genes suppressed by Src and induced by contact normalization. These genes encode growth factor receptors, adaptor proteins, and products that have not yet been annotated and may play important roles in tumor cell growth and migration.     

Contact behaviour exhibited by migrating neural crest cells in confrontation culture with somitic cells

Summary When grown in confrontation culture on a planar substratum, avian neural crest cells and somite cells display both homotypic and heterotypic contact inhibition of movement as judged by analysis of time-lapse video recordings of locomotory and contact behaviour, and by use of a nuclear overlap assay. It is therefore unlikely that migration of neural crest cells within the embryo, and within embryonic tissues, can be explained on the basis of a lack of contact inhibition. The results are discussed in the general context of cell invasiveness.     

Multi-scale modeling of a wound-healing cell migration assay

A continuum model and a discrete model are developed to capture the population-scale and cell-scale behavior in a wound-healing cell migration assay created from a scrape wound in a confluent cell monolayer. During wound closure, the cell population forms a sustained traveling wave, with close contact between cells behind the wavefront. Cells exhibit contact inhibition of migration and contact-limited proliferation. The continuum model includes the two dominant mechanisms and characteristics of cell migration and proliferation, using a cell diffusivity function that decreases with cell density and a logistic proliferative growth term. The discrete model arises naturally from the continuum model. Individual cells are simulated as continuous-time random walkers with nearest-neighbor transitions, together with a birth/death process. The migration and proliferation parameters are determined by analysing individual mice 3T3 fibroblast cell trajectories obtained during the development of a confluent cell monolayer and in a wound healing assay. The population-scale model successfully predicts the shape and speed of the traveling wave, while the discrete model is also successful in capturing the contact inhibition of migration effects.     

Cell-cell dissociation upon epithelial cell scattering requires a step mediated by the proteasome.

During development, tissue repair, and tumor metastasis, both cell-cell dissociation and cell migration occur and appear to be intimately linked, such as during epithelial "scattering." Here we show that cell-cell dissociation during scattering induced by hepatocyte growth factor (HGF) or activation of the temperature-sensitive v-Src tyrosine kinase in MDCK cells can be blocked by inhibiting the proteasome with lactacystin and MG132. Although both proteins of the tight junction and the adherens junction redistributed during cell scattering, proteasome inhibitors largely prevented this process, resulting in the stabilization of Triton X-100-insoluble tight junction proteins as well as adherens junction proteins at sites of cell-cell contact. Proteasome inhibition also led to a decrease of E-cadherin turnover in (35)S-labeled cells. In addition, proteasome inhibition partly preserved cell polarity, as determined by the subcellular distribution of Na(+),K(+)-ATPase (basolateral marker) and gp135 (apical marker), and the structure of the subcortical actin ring, both of which are normally disrupted during scattering. However, cells were able to establish focal contacts, and single cell migration toward HGF was unaffected by proteasome inhibition in quantitative assays, indicating that cell-cell dissociation during scattering occurs independently of anchorage-dependent cell migration. Thus, a proteasome-dependent step during scattering induced by HGF and pp60(v-Src) appears to be essential for cell-cell dissociation, disassembly of junctional components, and (at least indirectly) it also plays a role in the loss of protein polarity.     

The effect of fibrin on endothelial cell migration in vitro

Endothelial cells are known to migrate and come into contact with fibrin during numerous physiological processes, such as in wound healing and in tumor growth. The present study was initiated to investigate the effect of fibrin on endothelial cell migration in vitro. Endothelial cell migration was assayed by wounding confluent monolayers of bovine aortic endothelial cells with a razor blade and counting the number of cells crossing the wound per unit time. Wound-induced proliferation of endothelial cells was inhibited by mitomycin C-treatment without affecting endothelial cell migration, indicating that in this assay migration could be measured independent of proliferation. Migration of endothelial cells in vitro was inhibited by fibrin in a concentration dependent manner. Endothelial cell migration under fibrin was further reduced by plasminogen depletion of the serum, and fibrin still inhibited the migration of mitomycin C-treated endothelial cells. Kadish et al. (Tissue and Cell, 11, 99, 1979) previously reported that fibrin did not affect EC migration in vitro. The inability to inhibit EC migration with fibrin appears to be due to their assay system which employed agarose, since pre-treating the wounded monolayer with agarose eliminated the inhibition of EC migration by fibrin. The present results indicate that EC migration in vitro can be used as a model system for studying the interaction of fibrin with EC.     

Endostatin inhibits VEGF-induced endothelial cell migration and tumor growth independently of zinc binding.

Endostatin, produced as recombinant protein in human 293-EBNA cells, inhibits the migration of human umbilical vein endothelial cells (HUVECs) in response to vascular endothelial growth factor (VEGF) in a dose-dependent manner and prevents the subcutaneous growth of human renal cell carcinomas in nude mice at concentrations and in doses that are from 1000- to 100 000-fold lower than those previously reported. The inhibition of migration is not affected by mutations which eliminate Zn or heparin binding and inhibition of tumor growth does not depend on Zn binding. The results of the migration assays suggest that endostatin causes a block at one or more steps in VEGF-induced migration, while VEGF in turn can cause a block of the inhibition by endostatin of VEGF-induced migration of HUVECs.     

The Calpain/Calpastatin System Has Opposing Roles in Growth and Metastatic Dissemination of Melanoma

Conventional calpains are ubiquitous cysteine proteases whose activity is promoted by calcium signaling and specifically limited by calpastatin. Calpain expression has been shown to be increased in human malignant cells, but the contribution of the calpain/calpastatin system in tumorigenesis remains unclear. It may play an important role in tumor cells themselves (cell growth, migration, and a contrario cell death) and/or in tumor niche (tissue infiltration by immune cells, neo-angiogenesis). In this study, we have used a mouse model of melanoma as a tool to gain further understanding of the role of calpains in tumor progression. To determine the respective importance of each target, we overexpressed calpastatin in tumor and/or host in isolation. Our data demonstrate that calpain inhibition in both tumor and host blunts tumor growth, while paradoxically increasing metastatic dissemination to regional lymph nodes. Specifically, calpain inhibition in melanoma cells limits tumor growth in vitro and in vivo but increases dissemination by amplifying cell resistance to apoptosis and accelerating migration process. Meanwhile, calpain inhibition restricted to host cells blunts tumor infiltration by immune cells and angiogenesis required for antitumor immunity, allowing tumor cells to escape tumor niche and disseminate. The development of highly specific calpain inhibitors with potential medical applications in cancer should take into account the opposing roles of the calpain/calpastatin system in initial tumor growth and subsequent metastatic dissemination.