Association Between Ligand-Induced Conformational Changes of Integrin alpha IIbbeta 3 and alpha IIbbeta 3-Mediated Intracellular Ca2+ Signaling

Platelet _IIb3 is a prototypic integrinand plays a critical role in platelet aggregation. Occupancy of_IIb3 with multivalent RGD ligands, suchas fibrinogen, induces both expression of ligand-induced binding sites(LIBS) and _IIb3 clustering, which arethought to be necessary for outside-in signaling. However, theassociation between LIBS expression and outside-in signaling remainselusive. In this study, we used various_IIb3-specific peptidomimetic compounds asa monovalent ligand instead of fibrinogen and examined the associationbetween LIBS expression and outside-in signaling such as_IIb3-mediated intracellularCa²⁺ signaling. Using a set of monoclonal antibodies(MoAbs) against LIBS, we showed that antagonists can be divided intotwo groups. In group I, antagonists can induce LIBS on both_IIb and ₃ subunits. In group II,antagonists can induce LIBS on the _IIb subunit, but noton the ₃ subunit. Inhibition studies suggested thatgroup I and group II antagonists interact with distinct but mutually exclusive sites on _IIb3. Neither group Inor group II antagonist increased intracellular Ca²⁺concentrations ([Ca²⁺]_i) in nonactivatedplatelets. All antagonists at nanomolar concentrations abolished theincrease in [Ca²⁺]_i in 0.03 U/mLthrombin-stimulated platelets, which is dependent on bothfibrinogen-binding to _IIb3 andplatelet-aggregation. However, only group I antagonists at higherconcentrations dose-dependently augmented the[Ca²⁺]_i increase, which is due toaggregation-independent thromboxane A₂ production. Thisincrease in [Ca²⁺]_i was not observed inthrombasthenic platelets, which express no detectable_IIb3. Thus, only the group I antagonists,albeit a monovalent ligand, can initiate_IIb3-mediated intracellular Ca²⁺ signaling in the presence of thrombin stimulation.Our findings strongly suggest the association between ₃LIBS expression and _IIb3-mediatedintracellular Ca²⁺ signaling in platelets.     

整合素αvβ3与肿瘤的分子显像及靶向治疗

整合素αvβ3是由2条多肽链组成的跨膜异二聚体糖蛋白.其在正常细胞表面低表达或不表达而在肿瘤细胞及肿瘤新生血管内皮细胞中高表达,这使得它成为肿瘤分子显像及治疗的靶位点.近年来多种针对整合素αvβ3的显像技术取得了长足进步:包括放射性核素的PET及SPECT显像,MRI 显像、超声显像及光学显像;以整合素αvβ3为靶点的靶向治疗包括单克隆抗体治疗、RGD肽类似物治疗及以整合素αvβ3为靶点的药物投放治疗.整合素ανβ3临床研究对开拓肿瘤诊断及治疗有着重要的意义.     

Three-dimensional model of the human platelet integrin alpha IIbbeta 3 based on electron cryomicroscopy and x-ray crystallography

Integrins are a large family of heterodimeric transmembrane signaling proteins that affect diverse biological processes such as development, angiogenesis, wound healing, neoplastic transformation, and thrombosis. We report here the three-dimensional structure at 20-A resolution of the unliganded, low-affinity state of the human platelet integrin alpha(IIb)beta(3) derived by electron cryomicroscopy and single particle image reconstruction. The large ectodomain and small cytoplasmic domains are connected by a rod of density that we interpret as two parallel transmembrane alpha-helices. The docking of the x-ray structure of the alpha(V)beta(3) ectodomain into the electron cryomicroscopy map of alpha(IIb)beta(3) requires hinge movements at linker regions between domains in the crystal structure. Comparison of the putative high- and low-affinity conformations reveals dramatic conformational changes associated with integrin activation.     

Expression and Prognostic Significance of CD151, c-Met,and Integrin alpha3/alpha6 in Pancreatic Ductal Adenocarcinoma

Background  

CD151, c-Met, and integrin alpha3/alpha6 are all involved in the hepatocyte growth factor (HGF)/c-Met signal pathway, which plays an important role in the malignant progression of tumors.     

Disruption of matrix metalloproteinase 2 binding to integrin alpha vbeta 3 by an organic molecule inhibits angiogenesis and tumor growth in vivo

Matrix metalloproteinase 2 (MMP2) can associate with integrin alpha(v)beta3 on the surface of endothelial cells, thereby promoting vascular invasion. Here, we describe an organic molecule (TSRI265) selected for its ability to bind to integrin alphav(v)beta3 and block alpha(v)beta3 interaction with MMP2. Although disrupting alpha(v)beta3/MMP2 complex formation, TSRI265 has no effect on alpha(v)beta3 binding to its extracellular matrix ligand vitronectin and does not influence MMP2 activation or catalytic activity directly. However, TSRI265 acts as a potent antiangiogenic agent and thereby blocks tumor growth in vivo. These findings suggest that activated MMP2 does not facilitate vascular invasion during angiogenesis unless it forms a complex with alpha(v)beta(3) on the endothelial cell surface. By disrupting endothelial cell invasion without broadly suppressing cell adhesion or MMP function, the use of compounds such as TSRI265 may provide a novel therapeutic approach for diseases associated with uncontrolled angiogenesis.     

Blockade of alpha v beta3 and alpha v beta5 integrins by RGD mimetics induces anoikis and not integrin-mediated death in human endothelial cells

Alpha v integrins are thought to play an important role in tumor angiogenesis. However, discrepancies between findings with Arg-Gly-Asp (RGD) mimetics, which block angiogenesis in animal models, and knockout mice, in which loss of some alpha v integrins enhances tumor angiogenesis, raise questions concerning the function of these integrins and the precise role of alpha v substrate mimetics in antiangiogenic therapies. We have examined the effects of a novel non-peptide RGD mimetic, S 36578-2, on human endothelial cells to elucidate its antagonist activity and to identify possible agonist functions. S 36578-2 is highly selective for alpha v beta3 and alpha v beta5 integrins and induces detachment, caspase-8 activation, and apoptosis in human umbilical endothelial cells (HUVECs) plated on vitronectin. Importantly, the compound has no effect on the morphology or survival of cells plated on interstitial matrix components such as fibronectin, and it does not potentiate the apoptotic process in suspended cells. Identical results were obtained with a cyclic RGD peptide with similar target specificity. In microvascular endothelial cells, S 36578-2-induced death was also linked to its antiadhesive effect, with established lines markedly more resistant than primary cultures to the antiadhesive and proapoptotic effects. Altogether, these findings have important implications for the development of this class of antiangiogenics.     

胃癌组织Mina53的表达及其临床病理意义

背景:Mina53是新近发现的一种由c-Myc诱导的核抗原,在结肠癌、食管癌等消化道肿瘤中高表达,可能参与了肿瘤的发生和发展。目前,Mina53在胃癌中的研究还相对较少。目的:探讨Mina53在胃癌发生、发展中的作用和临床病理意义。方法:收集胃癌手术标本68例,同期收集正常胃窦黏膜组织30例作为正常对照组。采用免疫组化技术检测Mina53、c-Myc、Ki-67的定位和表达情况,分析胃癌组织中Mina53与c-Myc、Ki-67表达,以及与胃癌主要临床病理特征的相关性。结果:Mina53、c-Myc和Ki-67在胃癌组织中的高表达率显著高于正常胃黏膜(63.2%对0%,P0.001;52.9%对0%,P0.001;55.9%对3.3%,P0.001)。胃癌组织中,Mina53与c-Myc、Ki-67的表达呈正相关(P0.001,P0.05)。Mina53高表达与患者的性别、年龄和肿瘤部位无关,而与病灶大小、分化程度、浸润深度、淋巴结转移、TNM分期相关(P0.01)。结论:Mina53在胃癌组织中表达增高,其表达与c-Myc和Ki-67呈正相关,并与胃癌的分化、浸润、转移等临床病理特征相关。Mina53可能参与了胃癌的发生和发展,并有望作为胃癌预后判断的标记物,为胃癌的基因治疗提供新的靶点。     

VEGF-C与VEGFR-3在胃癌组织中的表达及意义

目的 探讨VEGF-C与VEGFR-3在胃癌组织中的表达情况及其与胃癌临床病理特征的关系.方法 以7例正常胃黏膜为对照,采用免疫组化检测38例胃癌组织中VEGF-C与VEGFR-3的表达情况,并分析其与胃癌临床病理特征之间的关系.结果 38例胃癌组织中VEGF-C阳性率为63.2%(24/38),而VEGFR-3阳性率为71.1%(27/38),两者的阳性率均高于正常黏膜组织,差异均有显著性(P<0.05);二者在有淋巴结转移组的表达强度均高于无转移组(P<0.05),而与肿瘤的浸润、分化程度之间无明显差异(P>0.05);二者之间有相关性(P<0.01).结论 胃癌组织中存在VEGF-C与VEGFR-3的高表达,且均与淋巴结转移有关.     

RUNX3蛋白在人结直肠癌中的表达及其临床意义

背景:Runx3(runt相关转录因子3)基因是一种新发现的抑癌基因,近年研究发现Runx3异常表达与人类多种消化系肿瘤的发生密切相关。目的:研究人结直肠癌中RUNX3蛋白的表达,分析其表达与结直肠癌临床病理特征的关系。方法:以免疫组化方法检测90例结直肠癌患者的癌组织和癌旁组织中RUNX3蛋白的表达。结果:结直肠癌组织中RUNX3蛋白的阳性表达率(47.8%,43/90)显著低于癌旁结直肠黏膜组织(100%,P<0.05)。RUNX3蛋白的表达与结直肠癌患者的性别、年龄、肿瘤部位、大小和组织学类型无关(P>0.05),与肿瘤浸润深度、分化程度、Dukes分期和有无淋巴结转移有关(P<0.05),浸润越深、分化程度越低、Dukes分期越晚和有淋巴结转移的癌组织,RUNX3蛋白低表达越明显。结论:RUNX3蛋白的表达可能与结直肠癌的浸润、分化和转移相关,提示RUNX3蛋白表达下调可能对结直肠癌的发生、发展具有重要作用。     

CD151、c-Met及整合素α3、α6在胰腺导管腺癌中的表达及其与预后的关系

目的 探讨CD151、c-Met和整合紊α3、α6蛋白在胰腺导管腺癌中的表达及其与预后的关系.方法 用免疫组化法检测71例胰腺导管腺癌及10例正常胰腺组织中CD151、c-Met和整合素α3、α6蛋白的表达,分析它们与临床病理特征及患者预后的关系.结果 CD151、c-Met和整合素α3、α6在71例胰腺导管腺癌组织中的表达阳性率分别为81.69%(58/71)、69.01%(49/71)、69.01%(49/71)和84.51%(60/71),而正常胰腺组织均未表达.CD151和c-Met的表达与肿瘤的TNM分期、淋巴结转移显著相关(P值均<0.05).CD151的表达与c-Met及整合素α3、α6的表达呈正相关(r=0.583,P=0.000;r=0.457;P=0.000;r=0.671;P=0.000).单因素分析显示,CD151、c-Met、整合素α3和α6的表达与预后有关(P值均<0.05).多因素分析表明,CD151、c-Met是患者术后生存时间的独立预后因子.结论 CD151、c-Met及整合素α3、α6在胰腺癌的发展、转移及预后发挥重要作用,CD151、c-Met可考虑作为临床评价胰腺癌生物学行为及评估预后的指标.     

CDl51、c-Met及整合素仪α3、α6在胰腺导管腺癌中的表达及其与预后的关系

目的探讨CD蚓、c-Met和整合素仪3、拍蛋白在胰腺导管腺癌中的表达及其与预后的关系。方法用免疫组化法检测71例胰腺导管腺癌及10例正常胰腺组织中CD151、c-Met和整合素仪3、嘶蛋白的表达,分析它们与临床病理特征及患者预后的关系。结果CD151、c-Met和整合素仪3、面在71例胰腺导管腺癌组织中的表达阳性率分别为81．69％（58／71）、69．01％（49／71）、69．01％（49／71）和84．51％（60／71）,而正常胰腺组织均未表达。CD151和c-Met的表达与肿瘤的TNM分期、淋巴结转移显著相关（P值均〈0．05）。CD151,的表达与c-Met及整合素α3、α6的表达呈正相关（r=0．583,P=0．000;r=0．457;P=0．000;r=0．671;P=0．000）。单因素分析显示,CD151、c-Met、整合素α3和α6的表达与预后有关（P值均〈0．05）。多因素分析表明,CD151、c-Met是患者术后生存时间的独立预后因子。结论CD151、c-Met及整合素α3、α6在胰腺癌的发展、转移及预后发挥重要作用,CD151、c-Met可考虑作为临床评价胰腺癌生物学行为及评估预后的指标。     

凋亡相关基因survivin、bcl-2及caspase-3在胆囊癌中的表达及意义

目的探讨凋亡相关基因survivin、bcl-2及caspase-3在胆囊癌中的表达及其在胆囊癌发生、发展的可能作用及相互关系。方法应用免疫组织化学SABC法,检测39例胆囊癌组织、15例胆囊腺瘤组织和12例慢性胆囊炎组织中survivin、bcl-2及caspase-3表达情况,分析其与胆囊癌临床病理的关系,并探讨survivin、bcl-2及caspase-3表达在胆囊癌中的相关性。结果survivin在胆囊癌中的阳性表达率为71.8%,而在胆囊腺瘤及慢性胆囊炎中均无表达;bcl-2在胆囊癌中的表达阳性率为71.8%,而在胆囊腺瘤及慢性胆囊炎中均无表达;bcl-2在胆囊癌中的表达阳性率为38.5%,在胆囊腺瘤中为93.3%,在慢性胆囊炎中为8.3%,胆囊腺瘤bcl-2表达明显高于胆囊癌(P<0.01),胆囊癌bcl-2表达明显高于慢性胆囊炎组织(P<0.05)。caspase-3在胆囊癌中的表达阳性率为43.6%,胆囊腺瘤及慢性胆囊炎中caspase-3表达率均为100%。survivin表达与患者的临床病理无关。bcl-2及caspase-3的表达与胆囊癌患者的性别、年龄、肿瘤的大小无关,而阳性率在组织分化程度、不同Nevin分期组间差异有显著性(P<0.05)。survivin与bcl-2及caspase-3表达没有相关性(P>0.05),bcl-2与caspase-3表达具有良好的相关性(P<0.05)。结论survivin和bcl-2在胆囊癌中有较高表达,而caspase-3在胆囊癌中的表达下降;bcl-2与caspase-3可反映胆囊癌的某些临床病理特点;survivin、bcl-2及caspase-3共同调节胆囊癌细胞凋亡,进而影响胆囊癌的发生、发展。