腫瘤侵襲和轉(zhuǎn)移.ppt

第八章 腫瘤的侵襲和轉(zhuǎn)移,本文由醫(yī)學(xué)百事通高端醫(yī)生網(wǎng)志愿者醫(yī)師制作 /,腫瘤轉(zhuǎn)移的基本過(guò)程 腫瘤轉(zhuǎn)移的分子生物學(xué) 阻止腫瘤轉(zhuǎn)移存在問(wèn)題及發(fā)展方向,第一節(jié) 腫瘤轉(zhuǎn)移的基本過(guò)程,一、腫瘤侵襲（tumor invasion) 指惡性腫瘤細(xì)胞從其起源部位沿組織間隙向周?chē)＝M織擴(kuò)張性增生的過(guò)程。其標(biāo)志是腫瘤細(xì)胞突破基底膜 腫瘤侵襲生長(zhǎng)行為有以下特點(diǎn)： 侵襲的腫瘤細(xì)胞能侵占和排擠周?chē)＝M織，但瘤細(xì)胞并未與原瘤灶分離 對(duì)周?chē)＝M織的功能有干擾或破壞,二、腫瘤轉(zhuǎn)移（tumor metastasis) 個(gè)別瘤細(xì)胞能脫離原發(fā)腫瘤，通過(guò)侵潤(rùn)在周?chē)g質(zhì)中生長(zhǎng)，通過(guò)淋巴管或血管遷移至其他部位繼續(xù)增殖生長(zhǎng)，形成與原發(fā)腫瘤相同性質(zhì)的繼發(fā)腫瘤的全過(guò)程。 繼發(fā)灶可再增殖，繼發(fā)侵襲生長(zhǎng)和形成新的腫瘤，并進(jìn)一步發(fā)生轉(zhuǎn)移，產(chǎn)生繼續(xù)擴(kuò)散和轉(zhuǎn)移。 侵襲生長(zhǎng)是癌組織擴(kuò)張的先行活動(dòng)，轉(zhuǎn)移是瘤體達(dá)到一定數(shù)量和體積后才會(huì)出現(xiàn)的現(xiàn)象。轉(zhuǎn)移時(shí)伴有侵襲生長(zhǎng)，但侵襲生長(zhǎng)并不一定發(fā)生轉(zhuǎn)移，兩者相輔相成。,三、腫瘤的侵襲生長(zhǎng)和轉(zhuǎn)移過(guò)程,早期原發(fā)癌的生長(zhǎng) 腫瘤血管形成 腫瘤細(xì)胞脫落并侵入基質(zhì) 進(jìn)入脈管系統(tǒng) 癌栓的形成 繼發(fā)組織器官定位生長(zhǎng) 轉(zhuǎn)移癌繼續(xù)擴(kuò)散,（一）、逃脫局部控制和侵潤(rùn) 轉(zhuǎn)移的第一步就是破壞與鄰近細(xì)胞的聯(lián)系，擺脫鄰近細(xì)胞的控制，穿過(guò)基質(zhì)進(jìn)入血管和淋巴管。 1、腫瘤細(xì)胞的增殖和擴(kuò)張 2、腫瘤細(xì)胞的分離與脫落,細(xì)胞粘附性狀發(fā)生改變,正常細(xì)胞間的相互作用 細(xì)胞粘附：細(xì)胞-細(xì)胞， 細(xì)胞-細(xì)胞外基質(zhì) 粘附關(guān)系：同質(zhì)粘附-相同細(xì)胞間粘合 異質(zhì)粘附-不同細(xì)胞或與細(xì)胞外基 質(zhì)的粘合 粘附分子：同嗜粘合-粘合分子相同 異嗜粘合-粘合分子不同 癌細(xì)胞：同型識(shí)別的破壞和異型識(shí)別的變化是侵潤(rùn)和轉(zhuǎn)移癌的特點(diǎn),細(xì)胞外基質(zhì)降解酶系統(tǒng)： 降解細(xì)胞外基質(zhì)，形成一條侵潤(rùn)和轉(zhuǎn)移通路,絲氨酸蛋白酶：胰蛋白酶，凝血酶，纖溶酶，尿激酶型和組織型纖溶酶原激活因子，彈性蛋白酶 半胱氨酸蛋白酶 天冬酰氨蛋白酶 糖苷酶 基質(zhì)金屬蛋白酶,3、惡性腫瘤細(xì)胞的運(yùn)動(dòng)性和趨化性,癌細(xì)胞向鄰近周?chē)?xì)胞移動(dòng)，貼近受侵細(xì)胞表面，表現(xiàn)為癌細(xì)胞表面伸出許多偽足貼附于受侵細(xì)胞 癌細(xì)胞伸出偽足，阿米巴樣運(yùn)動(dòng)，向受侵組織細(xì)胞間隙生長(zhǎng)侵入,（二）、內(nèi)侵 指腫瘤細(xì)胞從癌組織脫落侵入到血管中,1、轉(zhuǎn)移途徑 （1）血路轉(zhuǎn)移 （2）淋巴路轉(zhuǎn)移 （3）體腔,血流轉(zhuǎn)移 一些腫瘤細(xì)胞可從原發(fā)部位分離脫落，浸透組織基底膜，穿透間質(zhì)內(nèi)血管壁 瘤細(xì)胞自血管壁游離，或形成細(xì)胞聚集體，脫落進(jìn)入血循環(huán)，在循環(huán)中的腫瘤細(xì)胞大部分被迅速清除 存活的瘤細(xì)胞則隨血循環(huán)運(yùn)行，到達(dá)靶器官，在該器官小血管內(nèi)與內(nèi)皮細(xì)胞粘附、滯留 腫瘤細(xì)胞聚集體可在血管腔內(nèi)增殖，或再穿過(guò)血管壁，先與細(xì)胞外基質(zhì)粘附，進(jìn)入靶器官實(shí)質(zhì)，同實(shí)質(zhì)細(xì)胞發(fā)生粘附，在該處生長(zhǎng)，形成微小轉(zhuǎn)移灶 微小轉(zhuǎn)移灶長(zhǎng)至一定體積時(shí)，瘤組織血管新生，獲得營(yíng)養(yǎng)，進(jìn)一步長(zhǎng)大，形成轉(zhuǎn)移瘤,特點(diǎn)： 動(dòng)脈壁較厚，不易被侵犯；靜脈和毛細(xì)血管壁薄，易侵犯；毛細(xì)血管內(nèi)皮細(xì)胞周期性脫落更新，暴露基底膜 需蛋白酶消化基底膜 血流是一個(gè)惡劣環(huán)境，進(jìn)入血流的癌細(xì)胞99以上會(huì)因機(jī)械壓力，蛋白水解酶，宿主免疫系統(tǒng)監(jiān)控而破壞 腫瘤細(xì)胞在血液中是以單個(gè)細(xì)胞或若干個(gè)癌細(xì)胞與淋巴細(xì)胞和附著的血小板形成復(fù)合物的方式運(yùn)輸 癌細(xì)胞與靶器官血管內(nèi)皮細(xì)胞發(fā)生黏附，內(nèi)皮細(xì)胞收縮，受損，暴露其下的基底膜，瘤細(xì)胞附著于基底IV型膠原上，轉(zhuǎn)移出血管,（2）淋巴路轉(zhuǎn)移,淋巴管特點(diǎn)： 淋巴管壁薄，無(wú)完整的基底膜，易被癌細(xì)胞附著和穿入 內(nèi)皮細(xì)胞間有暫時(shí)裂隙，利瘤細(xì)胞進(jìn)入 淋巴液流動(dòng)緩慢，在有外力作用下，易促進(jìn)管內(nèi)瘤細(xì)胞運(yùn)動(dòng),轉(zhuǎn)移路徑,癌細(xì)胞穿透上皮基底膜，侵入結(jié)締組織間隙 癌細(xì)胞開(kāi)始向淋巴管靠近，并接觸管壁 癌細(xì)胞穿過(guò)淋巴管內(nèi)皮基底膜屏障，進(jìn)入管腔內(nèi) 癌細(xì)胞在淋巴管內(nèi)移動(dòng) 癌細(xì)胞通過(guò)輸入淋巴管到達(dá)匯流區(qū)淋巴結(jié)，在淋巴結(jié)內(nèi)滯留 癌細(xì)胞在淋巴結(jié)內(nèi)繼續(xù)生長(zhǎng)，可破壞竇壁內(nèi)皮，穿出淋巴竇，然后在淋巴結(jié)實(shí)質(zhì)內(nèi)增埴，破壞淋巴結(jié)的正常結(jié)構(gòu)，終至全部為癌組織所取代,進(jìn)入淋巴管內(nèi)或淋巴結(jié)內(nèi)癌細(xì)胞有2種命運(yùn) 被血流中免疫T-cell,NK等殺死 極少數(shù)逃脫免疫殺傷并能快速生長(zhǎng),（3）體腔 腹膜和肺部的胸膜腔是轉(zhuǎn)移的主要部位 腹膜腔內(nèi)器官的癌癥易在腹膜中擴(kuò)散 腹腔內(nèi)癌細(xì)胞外侵到達(dá)器官表面，掙脫并被腹膜液攜帶或直接與腔內(nèi)其它位點(diǎn)接觸 肺部腫瘤或其它位點(diǎn)轉(zhuǎn)移來(lái)的轉(zhuǎn)移灶，都能植入肺周?chē)托啬ぶg的腔隙，產(chǎn)生胸膜滲出液,2、腫瘤轉(zhuǎn)移的器官選擇性,1889 Reget 提出“種子土壤”學(xué)說(shuō)，認(rèn)為腫瘤的轉(zhuǎn)移是特殊的腫瘤細(xì)胞（種子）在適宜的環(huán)境（土壤）中生長(zhǎng)發(fā)展的結(jié)果 1929 Ewing以器官的血液，淋巴的行流方向來(lái)解釋轉(zhuǎn)移的發(fā)生 乳腺癌的淋巴轉(zhuǎn)移至腋窩淋巴結(jié) 腸胃道惡性腫瘤血行轉(zhuǎn)移多經(jīng)門(mén)靜脈首先轉(zhuǎn)移至肝臟 下肢皮膚癌及惡性黑色素瘤轉(zhuǎn)移至腹股溝淋巴結(jié),（1）血液循環(huán)的結(jié)構(gòu)特征能部分決定轉(zhuǎn)移生長(zhǎng)的位點(diǎn) 來(lái)自內(nèi)臟的血液匯集于肝門(mén)靜脈，通過(guò)肝，由心臟經(jīng)肺重新分布 因此，肝和肺是癌轉(zhuǎn)移的常見(jiàn)位點(diǎn) （2）首先經(jīng)過(guò)的器官 從原發(fā)位點(diǎn)通過(guò)血管最先遇到的器官經(jīng)常是癌細(xì)胞繼發(fā)生長(zhǎng)的位點(diǎn) 肝是常見(jiàn)的轉(zhuǎn)移位點(diǎn) 肺是頭頸部癌癥的轉(zhuǎn)移位點(diǎn),腫瘤細(xì)胞轉(zhuǎn)移能力的影響因素 腫瘤細(xì)胞表面差異性 組織器官微環(huán)境差異 影響腫瘤轉(zhuǎn)移器官選擇性的相關(guān)因素,（三）、外侵 逃避血管內(nèi)的破壞，逃離并侵入新的環(huán)境,1、腫瘤細(xì)胞血管內(nèi)錨定黏附 當(dāng)癌細(xì)胞聚集體，淋巴細(xì)胞和血小板復(fù)合物黏附到毛細(xì)血管內(nèi)皮細(xì)胞上時(shí)，錨定在內(nèi)皮細(xì)胞表面 血小板與內(nèi)皮細(xì)胞表面的纖維蛋白原相互作用，并通過(guò)P-選擇素與內(nèi)皮聚糖蛋白相互作用 內(nèi)皮E-選擇素結(jié)合到癌細(xì)胞的聚糖蛋白上 腫瘤細(xì)胞和淋巴細(xì)胞上的41整合素，有利于癌細(xì)胞聚集體運(yùn)動(dòng)的停止，及與內(nèi)皮的連接,2、從血管逃逸 內(nèi)皮細(xì)胞回縮，暴露基底膜上的糖蛋白，癌細(xì)胞黏附其上，然后利用蛋白酶和糖苷酶將其消化 癌細(xì)胞前導(dǎo)邊緣交替黏附到基質(zhì)蛋白上，同時(shí)滯后的邊緣交替脫離基質(zhì)來(lái)完成遷移過(guò)程 基質(zhì)蛋白質(zhì)水解過(guò)程中釋放的肽段也可作為趨化因子，吸引其它癌細(xì)胞到這個(gè)區(qū)域,3、定位生長(zhǎng) 腫瘤細(xì)胞進(jìn)入繼發(fā)臟器的基質(zhì)后，并不意味轉(zhuǎn)移一定形成，只有當(dāng)侵入繼發(fā)臟器的腫瘤細(xì)胞增殖并長(zhǎng)大，才真正完成轉(zhuǎn)移 癌細(xì)胞在新的位點(diǎn)上增殖最初局限于直徑1mm，要擴(kuò)大生長(zhǎng)，必須形成新血管，來(lái)提供氧和營(yíng)養(yǎng) 4、轉(zhuǎn)移的休眠,第二節(jié) 腫瘤轉(zhuǎn)移的分子生物學(xué),一、基因調(diào)控下的腫瘤轉(zhuǎn)移 腫瘤轉(zhuǎn)移促進(jìn)基因 Bcl-2, Myc, ras, raf, erbB-2 腫瘤轉(zhuǎn)移抑制基因 Nm23, TIMP,1、 The nm23 gene family The first metastasis suppressor gene identified was nm23 Eight members of the human nm23 family have been reported and are found in multiple subcellular compartments.,2、 Biochemical functions nm23 proteins posses multiple biochemical functions Interaction with numerous proteins A NDPKinase activity DNA nuclease Serine or histidine protein kinase,3. Nucleoside diphosphate kinase activity The nm23-H1 gene product has been identified as the NDPKA isoform The nm23-H2 gene product has been identified as the NDPKB isoform NDPKs: catalyze the phosphorylation of nucleoside diphosphates to the corresponding nucleoside triphosphates, mainly at the expense of the ATP synthesized through oxidative phosphorylation,The ping pong mechanism involves a conserved histidine, namely histidene118 in human enzymes, as a phosphorylated intermediate. All the eucaryotic NDPKs are hexamers (trimers of parallel dimers).,4. The role of nm23 in tumor metastasis Interactions of NDPKs, with other proteins may be important in the regulation of the underlying biochemical mechanism by which NDPKs determine the metastatic fate of a tumor cell,Interaction with numerous protein Tiam1(a specific GEF for Rac1) NDPKA is able to regulate the activity of Rac1 NDPKA suppresses the activity of Tiam1 V-Src interacts with the N-terminal region of Tiam1, NDPKA could interfere with this binding , modulating the GEF acting of Tiam1 by control of its binding to the plasma membrane,Interactions regulating the activity of small GTPase NDPK regulates the MAPK pathway by modulating the phosphorylation site of the kinase suppressor of Ras (KSR) NDPKA functions as a GAP of Rad,Interaction with transcription factors,(2) Interaction with cytoskeletal protein NDPK modulates cell shape-dependent processes involved in development, cell proliferation, differentiation and invasion and metastasis of tumor cells preventing Rac/Rho activation by blocking the GDP-exchange function of Tiam1, by preventing Src to bind to Tiam1 by regulation the local GTP/GDP-blance in protein complexes modulating the phosphorylation of amino acid of IFs,(3) DNA nuclease A model: the transcriptional regulation was explained by an intrinsic nuclease-like activity of NDPK,NDPKB could cleave both linear and supercoiled double-stranded DNA at a sequence specific site, resulting in a covalently bound enzyme-DNA complex energy of this covalent bond could be used to religate the DNA,(4) serine, histedine protein kinase Histidine phosphorylation Phosphohistidine is formed by a N-P phosphoramidate bond . Phosphorylation of the 1 and 3 nitrogens has been detected. Histidine kinases form a phospho-histidine intermediate, which then transfers the phosphate to the substrate,nm23-H1 phosphorylation on Ksr serine 392, a 14-3-3 binding site, and on serine 434 in conjunction with the serine 392 mutation. Ksr is thought to be a scaffold molecule for the Erk Map kinase signaling pathway. Histidine kinase activity of nm23-H1 is required for inhibition of the Map kinase pathway and correlated with motility suppression.,二、黏附因子與腫瘤轉(zhuǎn)移,(一) cell junctions Many cells in tissues are linked to one another and to the extracellular matrix at specialized contact sites called cell junctions,Occluding junctions seal cells together in an epithelium in a way that prevents even small molecules from leaking from one side of the sheet to the other,2. Anchoring junctions Mechanically attach cells to their neighbors or to the extracellular matrix,(1). Connect the cytoskeleton of a cell either to the cytoskeleton of its neighbors or to the extracellular matrix,(2). Anchoring junctions occur in two functionally different forms Adherens junctions and desmosomes hold cells together and are formed by transmembrane adhesion proteins that belong to the cadherin family Focal adhesions and hemidesmosomes bind cells to the extracellular matrix and are formed by transmembrane adhesion proteins of the integrin family Adherens junctions and focal adhesions serve as connection sites for actin filaments Desmosomes and hemidesmosomes serve as connection sites for intermediate filaments,3. Communicating junctions Mediate the passage of chemical or electrical signals from one interacting cell to its partner Gap junctions allow small molecules to pass directly from cell to cell,A summary of the various cell junctions,(二) cell-cell adhesion To form anchoring junction, cells must first adhere Animal cells can assemble into tissue either in place or after they migrate Dissociated vertebrate cells can reassemble into organized tissues through selective cell-cell adhesion,CAMs cell adhesion molecules cell-cell adhesion molecules cell-matrix adhesion molecules Ca 2+ -dependent Ca 2+ -independent,1、Cadherins mediate Ca2+-dependent cell-cell adhesion,Structure The Ca2+ ions are positioned between each pair of cadherin repeats,locking the repeats together to form a stiff, rodlike structure: the more Ca2+ ions that are bound , the more rigid the structure is. If Ca2+ is removed, the extracellular part of the protein becomes floppy and is rapidly degraded by proteolytioc enzyme.,b. Cadherins mediate cell-cell adhesion by a homophilic mechanism,c. Cadherins are linked to the actin cytoskeleton by catenins,2、Selectins mediate transient cell-cell adhesion in the bloodstream Selectins are cell-surface carbohydrate-binding protein (lectins) that mediate a variety of transient, ca2+-dependent, cell-cell adhesion interactions in the bloodstream. L-selectin E-selectin P-selectin,3、Members of the Ig superfamily of proteins mediate Ca2+-independent cell-cell adhesion N-CAM (neural cell adhesion molecule) I-CAM(intercellular adhesion molecule),4、Integrins Binding most ECM proteins Integrins are transmembrane heterodimers,Integrins must interact with the cytoskeleton to bind cells to the extracellular matrix,Summary,（三）、the extracellular matrix of animals The matrix has a far more active and complex role in regulating the behavior of the cells that contact it, influencing the survival, development, migration, proliferation, shape, and function,（1）The extracelluar matrix is made and oriented by the cells within it Glycosaminoglycans (GAGS)/proteoglycans Fibrous proteins: collagen, elastin, fibronectin, laminin,1) Glycosaminoglycans/proteoglycans Glycosaminoglycan(GAG) chains occupy large amounts of space and form hydrated gels,Structure:,four groups: hyaluronan chondroitin and dermatan sulfate heparan sulfate keratan sulfate function: form porous hydrated gels fill most of extracellular space provide mechanical support to the tissue Co-receptors,hyluronan is thought to facilitate cell migration during tissue morphogenesis and repair,proteoglycans are composed of GAG chains covalently linked to a core protein,GAG chains may be highly organized in the extracellular matrix,2) Fibrous proteins collagens are the major proteins of the xetracellular matrix Secreted by connective tissue cells and a variety of other cell types Major component of skin and bone The most abundant protein in mammals,Structure,classification,The formation of a collagen fibril Collagens are secreted with a nonhelical extension at each end After secretion , fibrillar procollagen molecules are cleaved to collagen molecules, which assemble into fibrils Fibril-associated collagens help organize the fibrils,elastin gives tissues their elasticity,fibronectin is an extracellular protein that helps cells attach to the matrix,laminin,3. Basal laminae are compose mainly of type IV collagen, laminin, nidogen, and a heparan sulfate proteoglycan,Function: separate cell to cell and tissue to tissue filtering roles determine cell polarity influence cell metabolism organize the proteins in adjacent plasma membrane promote cell survival, proliferation, differentiation serve as specific highway for cell migration The basal lamina is synthesized largely by the cells that on it Is tethered to the underlying connective tissue by specialized anchoring fibrils made of type VII collagen molecules,A model of the molecular structure of a basal lamina,4. The controlled degradation of matrix components helps cell migrate Cells migrate through a basal lamina, require degradation of matrix components matrix components are degraded by extracellular proteolytic enzymes (proteases) that are secreted locally by cells The proteolysis of matrix proteins can contribute to cell migration in several ways It can simply clear a path through the matrix It can expose cryptic sites on the cleaved proteins that promote cell binding, cell migration or both It can promote cell detachment so that a cell can move onward It can release extracellular signal proteins that stimulate cell migration,(四)、cadherins,Cadherin comprise an important group of cell-cell adhesion molecules that mediate intercellular adhesion by Ca2+-dependent homophilic interactions. By forming homedimers, cadherin can cluster through a zipper-like mechanism, while their intracellular domain is anchored to the actin cytoskeleton through and catenin.,1、cadherins （1）、Classification more than 80 members of the cadherin superfamily have been identified in the human genome. Including: classic cadherins, fat-like cadheins, seven-pass transmembrane cadherins Classic cadherins: E-, N-, P-,cadherin A subfamily of cadherins that share a common primary structure and bind to cateins through conserved cytoplasmic domains.,Fat-like cadherins: FAT-1 and FAT-2 A subfamily of cadherins that contain large tandem arrays(19-34) of extracellular cadherin domain and an EGF domain. Seven-pass transmembrane cadherins: A subfamily of cadherins that show some similarity to the secretin family of G-protein-linked receptors and contain eight to nine extracellular cadherin domains, two globin domains and four EGF domains. Also present is a domain called the Flamingo box, which is located between the last extracellular cadherin domain and the first EGF domain and is highly conserved across species in this subfamily.,Cadherins are traditionally calssified according to the tissue distribution or to the origin from which they discovered. the cadherin seen in epithelial cells is named as E-CD In heart as H-CD In neural tissues as N-CD Most of the cadherins are found in a variety of tissues. These cadherins are therefore reclassified according to the structural and functional similarities which they share, as cadherin 1-12,（2） Structure Extracellular CD domain: 5 tandem repeats, mediate Ca2+-dependent homophilic interactions: from disordered cadherin structure to a rigid rod-like structure (cis dimer) and then a trans dimer of multiple cis dimers, the trans dimers forming zipper structure Transmembrane domain: 35 aa Cytoplasmic domain of classic CDs: two portions,（3）E-CD The human E-CD gene(CDH1) is situated on chromosome 16q22.1 E-CD forms from a 135KD precursor that undergoes cytoplasmic trimming of what will become the extracellular N-terminal end of the mature molecule The mature E-CD,weighting approximately 120KD,The first catenin to interact with E-CD is -catenin Followed by binding of -catenin to a short region close to NH2-terminal of - catenin At last, forming stable bonds between the complex and the actin cytoskeleton P120ctn is responsible for modulation of CD clustering and thus the stabilization of adhesion,2、catenins Catenins are a group of cytoplasmic proteins which interact with the intracellular domain of the cadherin molecule, providing anchorage to the microfilament cytoskeleton. -catenin 102KD -catenin 88KD -catenin (plakoglobin) 82KD P120ctn 120KD,3、Two distinct E-CD-catenin complex E-CD, -catenin and -catenin E-CD, -catenin and -catenin,4、the relationship between regulation of E-CD-catenin complex and tumor metastasis （1）External factors regulate E-CD-catenin complex The interference with complex assembly seems to be mediated by a mitogenic signal transmitted by EGFR through its tyrosine kinase resulting in tyrosine phosphorylation of - catenin and E-CD itself. The end result is dissociation of - catenin from E-CD-catenin complex and translocation of free - catenin to the cytosolic pool,（2）Members of the small GTPase family regulate E-CD-catenin complex,Regulation of Rho-family GTPases The small GTPase family: the Ras the Rho subfamily: Rho, Rac1, cdc42,Possible modes of action of Rho GTPase in the regulation of E-cadherin-mediated cell-cell adhesion Rac1/Cdc42 and IQGAP1 can regulate E-CD activity IQGAP1 is localized to sites of cell-cell contact and it negatively regulates E-CD-mediated cell-cell adhesion by interacting with - catenin, with causes -catenin to dissociate from the cadherin-catenin complex Activated Rac1 and Cdc42 positively regulate cadherin-mediated cell-cell adhesion by inhibiting the interaction of IQGAP1 with - catenin,E-CD exists in dynamic equilibrium between the E-CD- - catenin- -catenin complex and the E-CD- - catenin- IQGAP1 complex at sites of cell-cell cntact When the amounts of activated Rac1 and Cdc42 increase binging to IQGAP1 inhibiting the interaction of IQGAP1 with - catenin the E-CD- - catenin- -catenin complex is high Strong adhesion activity When the amounts of inactivated Rac1 and Cdc42 increase IQGAP1 is free Intercating with - catenin to dissociate -catenin from the cadherin-catenin complex the E-CD- - catenin- IQGAP1 complex is high Resulting in weak adhesion abd cell-cell dissociation,Cadherin recycling E-CD cleavage by metalloproteinases,（3） Wnt-1 signaling pathway The increased pool of - catenin, have an effect on cell adhesion with the - catenin in the cytosolic pool either linking with E-CD or acting in the Wnt-1 pathway the - catenin combine with LEF/TCF, causing transcription of the cyclinD1 gene and downregulation of the CDH1 gene. The net result of all these interaction is a reduction in E-CD-mediated cell adhesion and proliferation of cells.,（4）、 summary,（5）、The role hypoxia in E-CD regulation and metastasis,5、changes of cadherin complex in cancer,Reduction in cell adhesion is of major importance in tumor metastasis and appears to be achieved by a variety of mechanisms affecting the E-CD-catenin complex Including: Reduced level of CD Abnormal location of E-CD Mutation of E-CD Shedding of E-CD Mutation and abnormal level of - catenin Abnormalities of - catenin Change of - catenin binding partners Changes of protein phosphorylation E-CD complex is directly involved in the benign to malignent transition,（五）、integrins,Integrins are heterodimeric (/ subunits) cell surface glycoproteins that bind to ECM proteins outside of the cell, and connect ,via their cytoplasmic domains,to components of the actin cytoskeleton within the cell. Members of the integrin family of cell adhesion receptors influence several important accepts of cancer cell behavior, including motility and invasiveness, cell growth and cell survival,1.structure and function,（1）、Structure Three are at least 18 subunits and 8subunits , giving rise to more then two dozen distinct integrins in mammalian cells Integrin is a heterodimer: A large extracellular ligand-binding domain A single transmembrane domain A small cytoplasmic domain （2）、function Integrins act as the bridge between EC