Integrin αvβ6 Promotes Lung Cancer Proliferation and Metastasis through Upregulation of IL-8–Mediated MAPK/ERK Signaling

Lung cancer is notorious for high morbidity and mortality around the world. Interleukin (IL)-8, a proinflammatory chemokine with tumorigenic and proangiogenic effects, promotes lung cancer cells growth and migration and contributes to cell aggressive phenotypes. Integrin αvβ6 is a receptor of transmembrane heterodimeric cell surface adhesion, and its overexpression correlates with poor survival from non–small cell lung cancer. However, the cross talk between αvβ6 and IL-8 in lung cancer has not been characterized so far. Herein, human lung cancer samples were analyzed, and it revealed that the immunohistochemical and mRNA expression of integrin αvβ6 was significantly correlated with the expression of IL-8. Furthermore, in vitro, integrin αvβ6 increased cell proliferation, migration, and invasion by impairing the expressions of MMP-2 and MMP-9 and inhibited cell apoptosis in human lung cancer cells A549 and H460. In addition, integrin αvβ6 upregulated IL-8 expression through activating MAPK/ERK signaling. The in vivo experiment showed that integrin αvβ6 promoted tumor growth in xenograft model mice by accelerating tumor volume and reducing apoptosis. Meanwhile, lung metastasis model experiment suggested that integrin αvβ6 stimulated tumor metastasis with the increase of lung/total weight and tumor nodules. Simultaneously, integrin αvβ6 upregulated IL-8 expression detected by both Western blots and immunohistochemistry, along with the activation of MAPK/ERK signaling. Overall, these data suggested that, in vitro and in vivo, integrin αvβ6 promoted lung cancer proliferation and metastasis, at least in part, through upregulation of IL-8–mediated MAPK/ERK signaling. Thus, the inhibition of integrin αvβ6 and IL-8 may be the key for the treatment of lung cancer.     

Integrin cleavage facilitates cell surface-associated proteolysis required for vascular smooth muscle cell invasion

Vascular smooth muscle cell (VSMC) invasion is a key element in atherogenesis and restenosis, requiring integrins for adhesion/de-adhesion as well as matrix metalloproteinases (MMPs) for focalized proteolysis. Among the MMP family, pro-MMP-2 is unique in its activation, depending on the formation of a multiprotein complex with MT1-MMP/TIMP-2 at the cell surface, in which integrin αvβ3 participates. Integrin αv and MT1-MMP are synthesized from precursors via furin-dependent cleavage of their pro-peptide. Furin is the prototypical proprotein convertase highly expressed in VSMCs and human atherosclerotic lesions. Its precise role in the tight network involving MMPs/integrins and their coordination and cooperation required for VSMC invasion is unknown. We demonstrate that furin-inhibition with decanoyl-RVKR-chloromethylketone inhibits VSMC invasion in a comparable degree to MMP inhibitors, which reduce the MT1-MMP–MMP-2 proteolytic cascade. Furin-inhibition did not prevent MT1-MMP/MMP-2 maturation. In contrast, it strongly reduced pro-αv cleavage, but did not lessen its cell membrane expression. However, inhibition of pro-αv processing via furin-inhibition strongly reduced pro-MMP-2 binding to the cell surface, thereby lessening its full maturation and diminishing the cell surface in situ proteolysis required for invasion. Thus, our data demonstrate a novel mechanism of furin-dependent αv cleavage that enhances pro-MMP-2 binding and activation at the cell membrane in cooperation with MT1-MMP in primary VSMCs. Processing of αv by furin contributes to the recruitment of enzymatic energy to the cell surface, thereby providing focalized proteolysis associated with VSMC invasion.     

Tumor suppressor KAI1 affects integrin αvβ3-mediated ovarian cancer cell adhesion, motility, and proliferation

The tetraspanin KAI1 had been described as a metastasis suppressor in many different cancer types, a function for which associations of KAI1 with adhesion and signaling receptors of the integrin superfamily likely play a role. In ovarian cancer, integrin αvβ3 correlates with tumor progression and its elevation in vitro provoked enhanced cell adhesion accompanied by significant increases in cell motility and proliferation in the presence of its major ligand vitronectin. In the present study, we characterized integrin αvβ3-mediated tumor biological effects as a function of cellular KAI1 restoration and proved for the first time that KAI1, besides its already known physical crosstalk with β1-integrins, also colocalizes with integrin αvβ3. Functionally, elevated KAI1 levels drastically increased integrin αvβ3/vitronectin-dependent ovarian cancer cell adhesion. Since an intermediate level of cell adhesive strength is required for optimal cell migration, we next studied ovarian cancer cell motility as a function of KAI1 restoration. By time lapse video microscopy, we found impaired integrin αvβ3/vitronectin-mediated cell migration most probably due to strongly enhanced cellular immobilization onto the adhesion-supporting matrix. Moreover, KAI1 reexpression significantly diminished cell proliferation. These data strongly indicate that KAI1 may suppress ovarian cancer progression by inhibiting integrin αvβ3/vitronectin-provoked tumor cell motility and proliferation as important hallmarks of the oncogenic process.     

Inhibition of platelets and tumor cell adhesion by the disintegrin domain of human ADAM9 to collagen I under dynamic flow conditions

This work aimed to investigate the role of the disintegrin domain of the human ADAM9 (ADAM9D) on the adhesion of breast tumor cells and platelets to collagen I, in a dynamic flow assay to simulate in vivo shear conditions. Recombinant ADAM9D was able to support tumor cell adhesion through binding to the β1 integrin subunit and also to inhibit the invasion through matrigel in vitro. In a dynamic flow assay ADAM9D inhibited about 75% and 65% of MDA-MB-231 tumor cells and platelet adhesion to collagen I, respectively. In addition, it was demonstrated that αVβ3 integrin is new interacting partner for ADAM9D. In conclusion, these results suggest a role for the disintegrin domain of ADAM9 in the metastatic process. Also, ADAM9D may be a tool for investigating the role of ADAMs in metastasis and cancer progression and for the design of selective inhibitors against the adhesion and extravasation of cancer cells.     

Stromal cell-derived factor-1 (SDF-1) enhances cells invasion by αvβ6 integrin-mediated signaling in ovarian cancer

Ovarian carcinoma is a common gynecological malignancy and a great threat to health as a result of metastasis. The chemokine stromal-derived factor (SDF-1) plays multiple roles in tumor pathogenesis. However, the precise molecular mechanism underlying SDF-1-induced ovarian cancer cell invasion is still undefined. αvβ6 integrin is an important factor in tumor progression. Therefore, we speculate that SDF-1-enhanced ovarian cancer cell invasion is related to αvβ6 integrin-mediated signaling. After culturing with SDF-1, an obvious time- and dose-dependent increase in αvβ6 integrin was demonstrated. Furthermore, CXC receptor 4 (CXCR4) was responsible for SDF-1-induced αvβ6 integrin expression. Simultaneously, SDF-1 was found to dramatically enhance extracellular matrix degradation via urokinase-type plasminogen activator (uPA) expression and cell invasion by αvβ6 integrin expression; these reinforce failed to be increased when pretreatment was performed with the CXCR4 inhibitor AMD3100 or anti-αvβ6 integrin antibody, respectively. In addition, αvβ6 integrin induced the phosphorylation of p38 MAPK and PI3 K/Akt, contributing to the up-regulation of uPA, as treatment with the specific inhibitor for p38 mitogen-activated protein kinases (MAPK) (SB203580) or phosphatidylinositol 3-kinase (PI3 K)/Akt (LY294002) strikingly abrogated uPA expression. Taken together, these results demonstrated that SDF-1 enhanced ovarian cancer cell invasion through αvβ6 integrin-mediated uPA expression via the p38 MAPK and PI3 K/Akt pathway. Consequently, our findings will provide a new explanation about how SDF-1 aggravates the pathogenesis of ovarian cancer.     

TIMP-1 interaction with αvβ3 integrin confers resistance to human osteosarcoma cell line MG-63 against TNF-α-induced apoptosis

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine affecting diverse cellular responses. TNF-α is cytotoxic in many systems, but it can also act as an anti-apoptotic signal to promote cell survival pathways activated through integrins and extracellular matrix components. This is particularly evident in cancer cells. To unravel the basis of resistance to TNF-α-induced apoptosis, human osteosarcoma MG-63 cell line was used. Our data showed that resistance to apoptosis was accompanied by high levels of TIMP-1 expression in part mediated by NF-κB activation, whereas under apoptotic conditions, in the presence of cycloheximide (CHX), TIMP-1 and αvβ3 integrin protein levels were significantly reduced. Silencing TIMP-1 using siRNA led to increased apoptosis following treatment with TNF-α, whereas exogenously-added recombinant TIMP-1 reduced the extent of apoptosis. Immunoprecipitation and confocal microscopy experiments demonstrated that TIMP-1 interacted with αvβ3 integrins. The biological role of this interaction was revealed by the use of echistatin, an antagonist of αvβ3 integrin. In the presence of echistatin, decreased protection against apoptosis by recombinant TIMP-1 was observed.     

Vascular endothelial growth factor A (VEGF-A) induces endothelial and cancer cell migration through direct binding to integrin {alpha}9{beta}1: identification of a specific {alpha}9{beta}1 binding site

Integrin α9β1 mediates accelerated cell adhesion and migration through interactions with a number of diverse extracellular ligands. We have shown previously that it directly binds the vascular endothelial growth factors (VEGF) A, C, and D and contributes to VEGF-induced angiogenesis and lymphangiogenesis. Until now, the α9β1 binding site in VEGF has not been identified. Here, we report that the three-amino acid sequence, EYP, encoded by exon 3 of VEGF-A is essential for binding of VEGF to integrin α9β1 and induces adhesion and migration of endothelial and cancer cells. EYP is specific for α9β1 binding and neither requires nor activates VEGFR-2, the cognate receptor for VEGF-A. Following binding to EYP, integrin α9β1 transduces cell migration through direct activation of the integrin signaling intermediates Src and focal adhesion kinase. This interaction is biologically important because it mediates in vitro endothelial cell tube formation, wound healing, and cancer cell invasion. These novel findings identify EYP as a potential site for directed pharmacotherapy.     

FAS1 Domain Protein Inhibits VEGF165-Induced Angiogenesis by Targeting the Interaction between VEGFR-2 and αvβ3 Integrin

It is known that VEGF receptors (VEGFR) and integrins interact with each other to regulate angiogenesis. We reported previously that the fasciclin 1 (FAS1) domain-containing protein, TGFBIp/βig-h3 (TGF-β-induced protein) is an angiogenesis regulator that inhibits both endothelial cell migration and growth via αvβ3 integrin. In an attempt to target the interaction between VEGFR-2 and αvβ3 integrin, we determined whether the FAS1 domain region of TGFBIp/βig-h3 (FAS1 domain protein) can block the interaction between the two receptors, leading to the suppression of angiogenesis. In this study, we showed that FAS1 domain protein inhibits VEGF(165)-induced endothelial cell proliferation and migration via αvβ3 integrin, resulting in the inhibition of VEGF(165)-induced angiogenesis. We also defined a molecular mechanism by which FAS1 domain protein blocks the association between αvβ3 integrin and VEGFR-2, showing that it binds to αvβ3 integrin but not to VEGFR-2. Blocking the association of these major angiogenic receptors with FAS1 domain protein inhibits signaling pathways downstream of VEGFR-2. Collectively, our results indicate that FAS1 domain protein, in addition to its inhibitory effect on αvβ3 integrin-mediated angiogenesis, also inhibits VEGF(165)-induced angiogenesis. Thus, FAS1 domain protein can be further developed into a potent anticancer drug that targets two principal angiogenic pathways. Mol Cancer Res; 10(8); 1010-20. ?2012 AACR.     

Switch from αvβ5 to αvβ6 integrin is required for CD9-regulated keratinocyte migration and MMP-9 activation

Our previous research found that tetraspanin CD9 is downregulated in migrating epidermis during wound healing, and CD9 downregulation contributes to keratinocyte migration via matrix metalloproteinase-9 (MMP-9) activation. However, little is known about the mechanisms involved in CD9-regulated keratinocyte migration and MMP-9 activation. In this study, we revealed that the expressions of integrin subunits β5 and β6 were regulated by CD9. Furthermore, CD9 silencing triggered the switch from αvβ5 to αvβ6 integrin in HaCaT keratinocytes and CD9 overexpression reversed the switch. Importantly, integrin αvβ6 functional blocking antibody 10D5 significantly inhibited CD9 silencing-induced keratinocyte migration and MMP-9 activation, suggesting that the switch from αvβ5 to αvβ6 integrin plays a key role in CD9-regulated cell migration and MMP-9 activation in keratinocytes.     

PKD Controls αvβ3 Integrin Recycling and Tumor Cell Invasive Migration through Its Substrate Rabaptin-5

Integrin recycling is critical for cell migration. Protein kinase D (PKD) mediates signals from the platelet-derived growth factor receptor (PDGF-R) to control αvβ3 integrin recycling. We now show that Rabaptin-5, a Rab5 effector in endosomal membrane fusion, is a PKD substrate. PKD phosphorylates Rabaptin-5 at Ser407, and this is both necessary and sufficient for PDGF-dependent short-loop recycling of αvβ3, which in turn inhibits α5β1 integrin recycling. Rab4, but not Rab5, interacts with phosphorylated Rabaptin-5 toward the front of migrating cells to promote delivery of αvβ3 to the leading edge, thereby driving persistent cell motility and invasion that is dependent on this integrin. Consistently, disruption of Rabaptin-5 Ser407 phosphorylation reduces persistent cell migration in 2D and αvβ3-dependent invasion. Conversely, invasive migration that is dependent on α5β1 integrin is promoted by disrupting Rabaptin phosphorylation. These findings demonstrate that the PKD pathway couples receptor tyrosine kinase signaling to an integrin switch via Rabaptin-5 phosphorylation.     

FAP-alpaha在胞外信号传递中与整合素的关系

目的：研究成纤维激活蛋白（Fibroblast Activation Protein,FAP）在促进卵巢癌细胞发生侵袭、迁移、增殖过程中与整合素α3β1、尿激酶型纤溶酶原激活剂受体（uPAR）的关系。方法：1）．免疫共沉淀共同检测整合素α3β1、uPAR在HO-8910PM上是否为二聚体。2）．transwell侵袭实验、迁移实验检测抑制整合素α3β1、uPAR后,卵巢癌细胞系HO-8910PM的侵袭迁移能力;3）．抑制整合素α3β1、uPAR后,再给予FAPet对HO-8910PM侵袭、迁移和增殖的影响。结果：1）．整合素α3β1、uPAR在HO-8910PM细胞外同一个位置表达;2）．抑制整合素α3β1能够明显抑制HO-8910PM的侵袭、迁移、增殖能力,并且可以抑制FAP对肿瘤的作用。3）．PAI—1抑制uPAR后,HO—8910PM的侵袭、迁移、增殖无明显变化,同时对FAP也无明显作用。结论：整合素α3β1和uPAR在HO-8910PM是一个复合体,FAPα,在细胞外是通过整合素α3β1传递信号进入细胞内而不是通过uPAR,整合素α3β1是通过uPAR与肿瘤细胞相连接。     

Blocking αvβ3 integrin by a recombinant RGD disintegrin impairs VEGF signaling in endothelial cells

Vascular endothelial growth factor (VEGF) and αvβ3 integrin are key molecules that actively participate in tumor angiogenesis and metastasis. Some integrin-blocking molecules are currently under clinical trials for cancer and metastasis treatment. However, the mechanism of action of such inhibitors is not completely understood. We have previously demonstrated the anti-angiogenic and anti-metastatic properties of DisBa-01, a recombinant His-tag RGD-disintegrin from Bothrops alternatus snake venom in some experimental models. DisBa-01 blocks αvβ3 integrin binding to vitronectin and inhibits integrin-mediated downstream signaling cascades and cell migration. Here we add some new information on the mechanism of action of DisBa-01 in the tumor microenvironment. DisBa-01 supports the adhesion of fibroblasts and MDA-MB-231 breast cancer cells but it inhibits the adhesion of these cells to type I collagen under flow in high shear conditions, as a simulation of the blood stream. DisBa-01 does not affect the release of VEGF by fibroblasts or breast cancer cells but it strongly decreases the expression of VEGF mRNA and of its receptors, vascular endothelial growth factor receptors 1 and 2 (VEGFR1 and VEGFR2) in endothelial cells. DisBa-01 at nanomolar concentrations also modulates metalloprotease 2 (MMP-2) and 9 (MMP-9) activity, the latter being decreased in fibroblasts and increased in MDA-MB-231 cells. In conclusion, these results demonstrate that αvβ3 integrin inhibitors may induce distinct effects in the cells of the tumor microenvironment, resulting in blockade of angiogenesis by impairing of VEGF signaling and in inhibition of tumor cell motility.     

Contortrostatin,a Homodimeric Disintegrin,Actively Disrupts Focal Adhesion and Cytoskeletal Structure and Inhibits Cell Motility Through a Novel Mechanism

Irttegrins play a major role in the regulation of cell motility. They physically link the extracellular environment to the cytoskeleton and participate in large protein complexes known as focal adhesions. In this report, it is demonstrated that treatment of tumor cells with the homodimeric disintegrin contortrostatin induces integrin-mediatcd tyrosine phosphorylation events and causes severe disruptions in the actin cytoskeleton and disassembly of focal adhesion structures without affecting cellular adhesion to a reconstituted basement membrane. Included in this disruption is the tyrosine phosphorylation and altered subcellular localization of FAK. Through use of transfected 293 cells with specific integrin expression profiles and anti-αvβ3 mAbs, we demonstrate that these events are mediated exclusively by the αvβ3 integrin and are likely the result of contortrostatin-mediated crosslinking of this receptor at the cell surface, since monovalent disintegrins, flavoridin or echistatin do not induce such effects. Further, it is shown that contortrostatin potently inhibits motility in cells expressing the αvβ3 integrin. The results of this study describe a novel integrin-mediated mechanism by which cell motility can be inhibited and suggest an alternative approach to therapeutic intervention for cancer invasion and metastasis.     

The snake venom disintegrin salmosin induces apoptosis by disassembly of focal adhesions in bovine capillary endothelial cells

Salmosin, a disintegrin purified from a Korean snake (Agkistrodon halys brevicaudus) venom, interacts with integrin alpha(v)beta(3) and inhibits the proliferation of bovine capillary endothelial (BCE) cells induced by basic fibroblast growth factor (bFGF). We investigated salmosin's mechanism of inhibition of BCE cell proliferation by examining changes in the cytoskeleton and activation of integrin-mediated signaling molecules. Salmosin disassembled cortical actins at focal adhesions and induced cells to be rounded and detached, but it did not alter microtubule structures in the early stage of cells being rounded. Immunolocalization of paxillin also demonstrated that focal adhesions were disassembled by salmosin. In salmosin-treated BCE cells, focal adhesion kinase (FAK) was dephosphorylated and expression of paxillin and p130(CAS) was decreased, but PI3 kinase, ILK, and beta-catenin were not expressed in decreased amounts or modified, suggesting that salmosin inactivated FAK-dependent integrin signaling pathways. While BCE cells proliferated normally on plates coated with salmosin, cells treated with salmosin eventually underwent apoptosis. These observations strongly suggest that salmosin disorganizes focal contacts to detach cells by competing with the extracellular matrix (ECM) for direct binding to integrin alpha(v)beta(3) on the cell surface, eventually leading to apoptosis.     

PTEN蛋白表达和明胶酶及其抑制因子在乳腺癌侵袭转移中的关系

目的研究乳腺癌中明胶酶(MMP-2、MMP-9)及其抑制物(TIMP-1)与抑癌基因PTEN产物PTEN蛋白的表达在肿瘤侵袭转移中的关系.方法应用免疫组织化学S-P法检测98例浸润性乳腺癌组织MMP-2、MMP-9及TIMP-1和PTEN蛋白的表达.结果乳腺癌MMP-2、MMP-9与PTEN表达呈显著负相关,而TIMP-1与PTEN蛋白表达呈显著正相关(P<0.05).在PTEN低表达组中,MMP-2、MMP-9的表达与腋窝淋巴结受累呈正相关;在PTEN高表达组中,MMP-2、MMP-9的表达与腋窝淋巴结受累呈正相关,TIMP-1与腋窝淋巴结受累呈负相关.结论在乳腺癌侵袭转移中MMP-2、MMP-9、TIMP-1与PTEN蛋白表达显著相关.MMP-2、MMP-9和TIMP-1对肿瘤细胞侵袭转移的作用可能在一定程度上受到PTEN的调控.     

Knockdown of TMEM14A expression by RNAi inhibits the proliferation and invasion of human ovarian cancer cells

Transmembrane protein 14A (TMEM14A) is a member of TMEMs. Alterations in TMEMs expression have been identified in several types of cancer, but the expression and function of TMEM14A in ovarian cancer is still unclear. Here, analysis on the expression data of the Cancer Genome Atlas (TCGA) ovarian serous cystadenocarcinoma (OV) dataset demonstrated the overexpression of TMEM14A in ovarian cancer tissues compared with normal tissues, which was consistent with our real-time PCR analysis on ovarian cancer and normal tissues collected from 30 patients. In addition, TMEM14A knockdown in two ovarian cancer cell lines, A2780 and HO-8910, reduced cell proliferation, causes cell cycle arrest and suppressed cell invasion. Moreover, silencing of TMEM14A notably repressed G1/S cell cycle transition and cell invasion via down-regulating the expression of cell cycle related proteins (Cyclin D1, Cyclin E and PCNA) and metastasis-related proteins (MMP-2 and MMP-9), respectively. TMEM14A knockdown significantly reduced the phosphorylation status of Smad2 and Smad3, downstream effectors of TGF-β signalling. In summary, these results indicate that TMEM14A has a pro-tumorigenic effect in ovarian cancer cells, suggesting an important role of this protein in ovarian cancer oncogenesis and metastasis.