An Interaction between Insulin-like Growth Factor-binding Protein 2 (IGFBP2) and Integrin α5 Is Essential for IGFBP2-induced Cell Mobility

Abstract

In the study we report here, we tested the hypothesis that insulin-like growth factor-binding protein 2 (IGFBP2) promotes cell mobility through its interaction with integrin α5. Our previous microarray studies showed that IGFBP2 activates the expression of integrin α5. In addition, IGFBP2 has an Arg-Gly-Asp (RGD) domain, which is a known integrin binding motif. We first confirmed our microarray results by showing that the expression of integrin α5 is indeed up-regulated at the protein level in IGFBP2-overexpressing SNB19 glioma cells. Using co-immunoprecipitation, we confirmed that IGFBP2 does interact with integrin α5. To confirm that IGFBP2 interacts directly with integrin α5 through the RGD domain, we created an RGD → RGE mutant (D306E) IGFBP2 and stably overexpressed the mutant IGFBP2 in the same cell line. Co-immunoprecipitation then showed that D306E-IGFBP2 had no detectable binding with integrin α5. We further observed that IGFBP2-overexpressing cells have extensive cell surface lamellipodia, whereas D306E-IGFBP2-overexpressing cells show abundant cell surface focal adhesions. Consistent with this, phenotype analysis then showed that IGFBP2-overexpressing cells have elevated migration rates compared with vector control; in contrast, the migration rates of the D306E-IGFBP2-overexpressing cells were not elevated and were comparable with that of vector control. Decreased expression of integrin α5 by small interference RNA in IGFBP2-overexpressing cells also reduced cell mobility. Therefore, we have concluded that one mechanism by which IGFBP2 activates IGFBP2-induced cell mobility is through its interaction with integrin α5 and this interaction is specifically mediated through the RGD domain on IGFBP2. In the study we report here, we tested the hypothesis that insulin-like growth factor-binding protein 2 (IGFBP2) promotes cell mobility through its interaction with integrin α5. Our previous microarray studies showed that IGFBP2 activates the expression of integrin α5. In addition, IGFBP2 has an Arg-Gly-Asp (RGD) domain, which is a known integrin binding motif. We first confirmed our microarray results by showing that the expression of integrin α5 is indeed up-regulated at the protein level in IGFBP2-overexpressing SNB19 glioma cells. Using co-immunoprecipitation, we confirmed that IGFBP2 does interact with integrin α5. To confirm that IGFBP2 interacts directly with integrin α5 through the RGD domain, we created an RGD → RGE mutant (D306E) IGFBP2 and stably overexpressed the mutant IGFBP2 in the same cell line. Co-immunoprecipitation then showed that D306E-IGFBP2 had no detectable binding with integrin α5. We further observed that IGFBP2-overexpressing cells have extensive cell surface lamellipodia, whereas D306E-IGFBP2-overexpressing cells show abundant cell surface focal adhesions. Consistent with this, phenotype analysis then showed that IGFBP2-overexpressing cells have elevated migration rates compared with vector control; in contrast, the migration rates of the D306E-IGFBP2-overexpressing cells were not elevated and were comparable with that of vector control. Decreased expression of integrin α5 by small interference RNA in IGFBP2-overexpressing cells also reduced cell mobility. Therefore, we have concluded that one mechanism by which IGFBP2 activates IGFBP2-induced cell mobility is through its interaction with integrin α5 and this interaction is specifically mediated through the RGD domain on IGFBP2. Cell migration is a highly regulated biological process and is associated with normal tissue modeling during early development. In most adult tissues, cell mobility is normally decreased but becomes highly active in cases of pathologic neoplasms, especially in advanced stages. This plus the increased production of basement membrane digestive enzymes are two key aspects of cancer invasion. Both are necessary for a cancer cell to successfully invade outside its original confines. With respect to cell mobility, cell surface receptors, such as integrins, must interact with the extracellular matrix in order for a cell to move. Participation of integrins in cell invasion has been shown to be critical in a wide variety of cancers (1Zheng D.Q. Woodward A.S. Fornarno M. Tallini G. Languino L.R. Cancer Res. 1999; 59: 1655-1664PubMed Google Scholar, 2Chung J. Bachelder R.E. Lipscomb E.A. Shaw L.M. Mercurio A.M. J. Cell Biol. 2002; 158: 165-174Crossref PubMed Scopus (171) Google Scholar, 3Nemeth J.A. Cher M.L. Zhou Z. Mullins C. Bhagat S. Trikha M. Clin. Exp. Metastasis. 2003; 20: 413-420Crossref PubMed Scopus (74) Google Scholar, 4Yang C. Zeisberg M. Lively J.C. Nyberg P. Afdhal N. Kalluri R. Cancer Res. 2003; 63: 8312-8317PubMed Google Scholar, 5Davidson B. Goldberg I. Reich R. Tell L. Dong H.P. Trope C.G. Risberg B. Kopolovic J. Gynecol. Oncol. 2003; 90: 248-257Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar). Once a signal is transmitted to the integrin receptor, a host of intracellular proteins are then activated and begin transmission of cascades of signals inside the cell. Aside from ligand binding, proteins are also able to interact with the integrin receptor inside the cell to modulate signaling and/or receptor affinity status, a process previously referred to as “inside-out” signaling (6O'Toole T.E. Katagiri Y. Faull R.J. Peter K. Tamura R. Quaranta V. Loftus J.C. Shattil S.J. Ginsberg M.H. J. Cell Biol. 1994; 124: 1047-1059Crossref PubMed Scopus (581) Google Scholar). Eventually, certain intracellular protein signals are turned on (e.g. small molecule GTPases), enabling cells to increase their mobility. These proteins produce cytoskeletal rearrangements, such as stress fiber and membrane ruffle formation, that are conducive to cell movement. Here, we are specifically interested in IGFBP2-mediated mechanisms of cell mobility that contribute to invasiveness. Gliomas are the most common primary tumors of the central nervous system, accounting for 80% of adult primary brain tumors (7De Girolami U. Anthony D.C. Frosch M.P. Cotran R.S. Kumar V. Collins T. Robbins Pathologic Basis of Disease. Saunders, Philadelphia1999: 1293-1357Google Scholar). Patients with the most advanced stage of glioma, glioblastoma multiforme (GBM), 2The abbreviations used are: GBM, glioblastoma multiforme; IGF, insulin-like growth factor; IGFBP2, IGF-binding protein 2; RGD, Arg-Gly-Asp domain; PBS, phosphate-buffered saline; siRNA, small interference RNA; TRITC, tetramethylrhodamine isothiocyanate. face a very poor clinical outlook. By the time patients show clinical symptoms of GBM, they face a median survival of 8–10 months at the time of diagnosis. The characteristic that makes GBM so devastating and therapeutically intractable is its highly micro-invasive nature. Single-cell invasiveness typically renders GBM surgically incurable and results in significant neurological morbidity, with death being the outcome for most patients. Previous studies using cDNA microarray profiling, followed by tissue microarray validation, have identified insulin-like growth factor-binding protein 2 (IGFBP2) overexpression as one of the most frequent molecular events in GBM (8Fuller G.N. Rhee C.H. Hess K.R. Caskey L.S. Wang R. Bruner J.M. Yung W.K. Zhang W. Cancer Res. 1999; 59: 4228-4232PubMed Google Scholar, 9Wang H. Zhang W. Fuller G.N. Brain Pathol. 2002; 12: 95-107Crossref PubMed Scopus (110) Google Scholar, 10Zhang W. Wang H. Song S.W. Fuller G.N. Brain Pathol. 2002; 12: 87-94Crossref PubMed Scopus (36) Google Scholar, 11Sallinen S.L. Sallinen P.K. Haapasalo H.K. Helin H.J. Helen P.T. Schraml P. Kallioniemi O.P. Kononen J. Cancer Res. 2000; 60: 6617-6622PubMed Google Scholar, 12Elmlinger M.W. Deininger M.H. Schuett B.S. Meyermann R. Duffner F. Grote E.H. Ranke M.B. Endocrinology. 2001; 142: 1652-1658Crossref PubMed Scopus (70) Google Scholar). Subsequent functional studies showed that IGFBP2 promotes GBM invasion by activating the expression of a series of cell adhesion and cell mobility genes (13Wang H. Wang H. Shen W. Huang H. Hu L. Ramdas L. Zhou Y.H. Liao W.S. Fuller G.N. Zhang W. Cancer Res. 2003; 63: 4315-4321PubMed Google Scholar). The specific signal transduction events through which IGFBP2 produces enhanced cell invasion remain unresolved. Although it is known that IGFBP2 activates the expression of matrix metalloprotease 2, which contributes to cell invasiveness by breaking down matrix, the mechanism by which IGFBP2 activates cell mobility remains unknown. Under normal physiological conditions, IGFBP2 is predominantly expressed in highly proliferative fetal tissues that exhibit extensive cell movement and tissue remodeling (14Green B.N. Jones S.B. Streck R.D. Wood T.L. Rotwein P. Pintar J.E. Endocrinology. 1994; 134: 954-962Crossref PubMed Scopus (93) Google Scholar). Within the central nervous system, IGFBP2 is expressed in fetal glial cells, but after birth its expression significantly decreases (15Lee W.H. Michels K.M. Bondy C.A. Neuroscience. 1993; 53: 251-265Crossref PubMed Scopus (121) Google Scholar). IGFBP2 is thus an important protein involved in cell movement during development. As is the case with many critical molecules in cancer biology, IGFBP2 has deviated from its normal role in the development of certain human cancers. In the present study, we seek to further elucidate the role of IGFBP2 in the context of cancer and also attempt to delineate a mechanism of IGFBP2 signal transduction that leads to glioma cell migration, a critical step in IGFBP2-induced cell invasion. We hypothesize that one mechanism by which IGFBP2 promotes cell mobility is through its interaction with integrins. We arrived at this hypothesis as a result of several observations. First, our previous microarray analyses of genes affected by IGFBP2 overexpression showed that IGFBP2 activates the expression of integrin α5. Second, a sequence analysis of the IGFBP2 protein revealed an Arg-Gly-Asp (RGD) domain (at codons 304–306), which is a well characterized integrin-binding domain (16Pierschnacher M.D. Ruoslahti E. Nature. 1984; 309: 30-33Crossref PubMed Scopus (2896) Google Scholar, 17Ruoslahti E. Pierschnacher M.D. Science. 1987; 238: 491-497Crossref PubMed Scopus (3894) Google Scholar). Insulin-like growth factor-binding protein 1 (IGFBP1) also contains an RGD domain in its protein sequence and has been shown to bind integrin (18Jones J.I. Gockerman A. Busby Jr., W.H. Wright G. Clemmons D.R. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 10553-10557Crossref PubMed Scopus (484) Google Scholar). The IGFBP1-integrin interaction was further found to activate human trophoblast cell migration (19Gleeson L.M. Chakraborty C. McKinnon T. Lala P.K. J. Clin. Endocrinol. Metab. 2001; 86: 2484-2493Crossref PubMed Scopus (197) Google Scholar). Two groups have independently reported that IGFBP2 interacts with integrins in two different cell lines, breast (20Pereira J.J. Meyer T. Docherty S.E. Reid H.H. Marshall J. Thompson E.W. Rossjohn J. Price J.T. Cancer Res. 2004; 64: 977-984Crossref PubMed Scopus (84) Google Scholar) and sarcoma (21Schutt B.S. Langkamp M. Rauschnabel U. Ranke M.B. Elmlinger M.W. Endocrinology. 2004; 32: 859-868Google Scholar); however, the effects of this interaction identified by the two groups were different. In breast cancer, it was found that IGFBP2 interacts with integrin αv and that this interaction reduced tumor cell migration (20Pereira J.J. Meyer T. Docherty S.E. Reid H.H. Marshall J. Thompson E.W. Rossjohn J. Price J.T. Cancer Res. 2004; 64: 977-984Crossref PubMed Scopus (84) Google Scholar). In sarcoma, IGFBP2 was found to interact with integrin α5, and although no direct cell migration analysis was performed, the interaction promoted tumor cell de-adhesion (21Schutt B.S. Langkamp M. Rauschnabel U. Ranke M.B. Elmlinger M.W. Endocrinology. 2004; 32: 859-868Google Scholar), which is a characteristic consistent with increased cell mobility. Thus, IGFBP2 interacts with different integrin subunits in different cells and/or under different physiological conditions, affecting cell adhesion and mobility. In this study, we examined GBM cells, which are well recognized for overexpressing both IGFBP2 (2Chung J. Bachelder R.E. Lipscomb E.A. Shaw L.M. Mercurio A.M. J. Cell Biol. 2002; 158: 165-174Crossref PubMed Scopus (171) Google Scholar, 3Nemeth J.A. Cher M.L. Zhou Z. Mullins C. Bhagat S. Trikha M. Clin. Exp. Metastasis. 2003; 20: 413-420Crossref PubMed Scopus (74) Google Scholar, 4Yang C. Zeisberg M. Lively J.C. Nyberg P. Afdhal N. Kalluri R. Cancer Res. 2003; 63: 8312-8317PubMed Google Scholar, 5Davidson B. Goldberg I. Reich R. Tell L. Dong H.P. Trope C.G. Risberg B. Kopolovic J. Gynecol. Oncol. 2003; 90: 248-257Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar, 6O'Toole T.E. Katagiri Y. Faull R.J. Peter K. Tamura R. Quaranta V. Loftus J.C. Shattil S.J. Ginsberg M.H. J. Cell Biol. 1994; 124: 1047-1059Crossref PubMed Scopus (581) Google Scholar) and integrin (22Gingras M.C. Roussel E. Bruner J.M. Branch C.D. Moser R.P. J. Neuroimmunol. 1995; 57: 143-153Abstract Full Text PDF PubMed Scopus (157) Google Scholar, 23Mahesparan R. M. R. 2003; PubMed Scopus Google Scholar) compared with normal We show that IGFBP2 interacts with integrin α5 through a specific binding domain on IGFBP2 and that this interaction is necessary for IGFBP2-mediated cell Cell and human GBM cells overexpressing IGFBP2 had been previously with a expression vector IGFBP2 cDNA and a using vector cell was also created by of an expression vector (13Wang H. Wang H. Shen W. Huang H. Hu L. Ramdas L. Zhou Y.H. Liao W.S. Fuller G.N. Zhang W. Cancer Res. 2003; 63: 4315-4321PubMed Google Scholar). These cells have been in with fetal in a at SNB19 cells were with a expression vector D306E-IGFBP2 cDNA and a using using and cells were in the of to the IGFBP2-overexpressing The expression of IGFBP2 in the SNB19 were by analyses of cell using The was using the with specifically used to the The sequence used for the is as → In to the by we of to the of the of the IGFBP2 were confirmed by Co-immunoprecipitation and the to cells were by by and Cell 1 of with at were then with and protein at were in phosphate-buffered after which the were for in and with α5 of the IGFBP2 and D306E-IGFBP2 proteins was by cells were by by and of proteins were for by in in PBS, and with the primary and α5 were with an enhanced confirm the of in IGFBP2-overexpressing cells, we a molecule affinity to of In this cell were with for 1 at to down the were and with by the were and by was with an To the a was on using the same were using The was In Cell and migration rates were using a migration in this case with an The of with fetal as the as a control. In this 2 were in in the and for 2 at in a with the cells that had through the the were and under a were in The in the cell migration rates and cell were using a the to confirm the cells were in they small was the of the well using a small were to at in a with were from the at time and were under a were and in the for were then in at for in for at for and with with from the for in was and the cells at the cells were with PBS, in was and the cells at for 1 the were with PBS, they were with with and with The was with the which focal adhesion a of cells, are present on the of the cell of α5 was SNB19 cells using the from the of was to be and a cell of well was used were to for and a sequence as a both by were in the at in a with for were then for protein expression and phenotype analysis migration IGFBP2 our microarray showed that integrin α5 was up-regulated in IGFBP2-overexpressing SNB19 cells (7De Girolami U. Anthony D.C. Frosch M.P. Cotran R.S. Kumar V. Collins T. Robbins Pathologic Basis of Disease. Saunders, Philadelphia1999: 1293-1357Google Scholar). We to confirm this at the protein level by analyses in several SNB19 cell stably with IGFBP2. the integrin α5 with the integrin we that integrin also be Thus, we the expression level of integrin as We found that both the α5 and subunits were up-regulated at the protein level in IGFBP2-overexpressing cell lines, although the α5 was to a level was the Thus, the expression of the integrin receptor is up-regulated IGFBP2 is our microarray IGFBP2 with the IGFBP2 protein an RGD domain, as shown by primary it is that IGFBP2 not the expression of integrin α5 but also interacts with integrin α5 the RGD We tested this interaction In IGFBP2-overexpressing cells, we IGFBP2 and then integrin α5 by In contrast, with not down integrin α5 IGFBP2 to α5 through the RGD the binding of IGFBP2 to integrin α5 through the RGD Using we an IGFBP2 expression vector with a in which was to thus the RGD domain to RGE We then the D306E-IGFBP2 mutant vector SNB19 cells and created We several D306E-IGFBP2 for D306E-IGFBP2 were that expressed mutant IGFBP2 at comparable with the IGFBP2 for in further in this Co-immunoprecipitation was with the D306E-IGFBP2 to the α5 binding D306E-IGFBP2 showed no detectable of integrin α5 compared with cells IGFBP2. D306E-IGFBP2-overexpressing and IGFBP2-overexpressing up-regulated integrin α5 protein expression to comparable not Thus, the in the of α5 binding were to the and not to a in the integrin α5 expression Therefore, not does IGFBP2 bind to integrin α5, but the interaction also to be mediated specifically through the integrin binding RGD on IGFBP2. of IGFBP2 with α5 in Cell observed in the cell that on the cells overexpressed IGFBP2 on for we focal adhesion on the of the cell membrane in and D306E-IGFBP2-overexpressing cells. In contrast, the IGFBP2-overexpressing cells were showing To confirm the of in IGFBP2-overexpressing cells, we for the of the small a molecule to This showed that IGFBP2-overexpressing cells D306E-IGFBP2-overexpressing cells. In IGFBP2-overexpressing cells showed a increase vector in the level We then for which showed in the of IGFBP2-overexpressing cells We also the of cells with cells for We the cells showing and found that a significantly of IGFBP2-overexpressing cells had vector and D306E-IGFBP2-overexpressing cells Thus, on the of our cell it that D306E-IGFBP2-overexpressing cells have a decreased compared with IGFBP2-overexpressing cells, and this was in the in the of IGFBP2 with α5 for IGFBP2-induced Cell the of IGFBP2 to interact with integrin α5 the of lamellipodia, we a cell migration to cell surface are associated with cell mobility. This showed that SNB19 cells overexpressing IGFBP2 significantly vector cells. SNB19 cells overexpressing D306E-IGFBP2 not in at the same as the SNB19 and vector cells confirmed the migration cells overexpressing IGFBP2 and cells overexpressing SNB19 cells overexpressing IGFBP2 and the in whereas vector and D306E-IGFBP2-overexpressing cells significantly to the Thus, the and both showed that D306E-IGFBP2-overexpressing cells and vector cells had a migration of α5 IGFBP2-induced Cell further confirm the of the interaction IGFBP2 and integrin α5 in IGFBP2-induced cell migration, we used to the expression of integrin α5 and examined the effects of integrin α5 in IGFBP2-overexpressing cells. α5 expression was reduced in the integrin α5 cells compared with the cells, IGFBP2 expression The cells were then for cell migration we found that the down of integrin α5 significantly the cell migration of the IGFBP2-overexpressing cells the in cell migration is to the decreased of integrin α5. The enhanced expression of IGFBP2 was found to be one of the most frequent in GBM (8Fuller G.N. Rhee C.H. Hess K.R. Caskey L.S. Wang R. Bruner J.M. Yung W.K. Zhang W. Cancer Res. 1999; 59: 4228-4232PubMed Google Scholar, 9Wang H. Zhang W. Fuller G.N. Brain Pathol. 2002; 12: 95-107Crossref PubMed Scopus (110) Google Scholar, 10Zhang W. Wang H. Song S.W. Fuller G.N. Brain Pathol. 2002; 12: 87-94Crossref PubMed Scopus (36) Google Scholar, 11Sallinen S.L. Sallinen P.K. Haapasalo H.K. Helin H.J. Helen P.T. Schraml P. Kallioniemi O.P. Kononen J. Cancer Res. 2000; 60: 6617-6622PubMed Google Scholar, 12Elmlinger M.W. Deininger M.H. Schuett B.S. Meyermann R. Duffner F. Grote E.H. Ranke M.B. Endocrinology. 2001; 142: 1652-1658Crossref PubMed Scopus (70) Google Scholar) and in advanced stage cancers of the E. T. T. E. L. E. 2003; PubMed Scopus Google Scholar, P. J. 2003; PubMed Scopus Google Scholar) and S. F. A. C. Clin. Cancer Res. 2004; PubMed Scopus Google Scholar, A. B. J. Clin. Endocrinol. Metab. PubMed Scopus Google Scholar). The that IGFBP2 is overexpressed in advanced of tumors that IGFBP2 functional critical in the of such as increased cell and invasion. In cancer, IGFBP2 was shown to cell S. J. 2004; PubMed Scopus Google Scholar, S. K. T. M. M. H. Cancer Res. 2003; 63: Google Scholar). In both brain and IGFBP2 has been found to tumor cell invasion but not cell (13Wang H. Wang H. Shen W. Huang H. Hu L. Ramdas L. Zhou Y.H. Liao W.S. Fuller G.N. Zhang W. Cancer Res. 2003; 63: 4315-4321PubMed Google Scholar, C. I. Wang H. J. A. J.J. Zhang W. PubMed Scopus Google Scholar). Although IGFBP2 is a of a of proteins known to modulate the of insulin-like growth the of proteins is This is several reported of also that are of These direct effects on migration, and of In this study, we that IGFBP2 the migration of GBM cells through its interaction with integrin this interaction is on the IGFBP2 RGD We used a GBM cell with a level of IGFBP2. overexpression of IGFBP2 is a common molecular found in GBM (8Fuller G.N. Rhee C.H. Hess K.R. Caskey L.S. Wang R. Bruner J.M. Yung W.K. Zhang W. Cancer Res. 1999; 59: 4228-4232PubMed Google Scholar, 9Wang H. Zhang W. Fuller G.N. Brain Pathol. 2002; 12: 95-107Crossref PubMed Scopus (110) Google Scholar, 10Zhang W. Wang H. Song S.W. Fuller G.N. Brain Pathol. 2002; 12: 87-94Crossref PubMed Scopus (36) Google Scholar, 11Sallinen S.L. Sallinen P.K. Haapasalo H.K. Helin H.J. Helen P.T. Schraml P. Kallioniemi O.P. Kononen J. Cancer Res. 2000; 60: 6617-6622PubMed Google Scholar, 12Elmlinger M.W. Deininger M.H. Schuett B.S. Meyermann R. Duffner F. Grote E.H. Ranke M.B. Endocrinology. 2001; 142: 1652-1658Crossref PubMed Scopus (70) Google Scholar), we to IGFBP2 in SNB19 cells this cell an GBM that was not overexpressing this integrin α5 is also expressed in in SNB19 cells. In our SNB19 cells, by overexpressing IGFBP2 overexpression of integrin we were able to the interaction two proteins and integrin In SNB19 cells, the IGFBP2 and integrin α5 also interact to a role in cell mobility. We further found in IGFBP2 in the decreased of focal which are Thus, the of IGFBP2 to integrin α5 contributes to the of the glioma cell to at the focal and a In SNB19 cells that IGFBP2, we observed increased of lamellipodia, to no focal and the of the cells to significantly compared with vector and D306E-IGFBP2-overexpressing cells. a molecule in the signal transduction that leads to the of lamellipodia, is and it to the of IGFBP2-overexpressing cells. in cells that we focal but no and a migration Although of was in cells overexpressing we observed activated in the D306E-IGFBP2 in the vector control. This that overexpression of IGFBP2 is able to activate of IGFBP2 to integrin α5. the mechanism through which IGFBP2 activates of integrin α5 remains to be the of our study, (20Pereira J.J. Meyer T. Docherty S.E. Reid H.H. Marshall J. Thompson E.W. Rossjohn J. Price J.T. Cancer Res. 2004; 64: 977-984Crossref PubMed Scopus (84) Google Scholar) and (21Schutt B.S. Langkamp M. Rauschnabel U. Ranke M.B. Elmlinger M.W. Endocrinology. 2004; 32: 859-868Google Scholar) also independently showed that IGFBP2 to integrins and regulated cell movement. The and the specific integrin however, to on the under In breast cancer, the interaction of IGFBP2 with integrin αv decreased cell migration (20Pereira J.J. Meyer T. Docherty S.E. Reid H.H. Marshall J. Thompson E.W. Rossjohn J. Price J.T. Cancer Res. 2004; 64: 977-984Crossref PubMed Scopus (84) Google Scholar). In the glioma cells that we used for this study, integrin αv is however, IGFBP2 not integrin αv not Thus, the interaction IGFBP2 and integrin proteins is through a mechanism that is not In addition, the IGFBP2 and the integrin subunits produce effects on cell In sarcoma cells, IGFBP2 has been shown to interact with integrin α5 and results in increased cell de-adhesion and reduced cell (21Schutt B.S. Langkamp M. Rauschnabel U. Ranke M.B. Elmlinger M.W. Endocrinology. 2004; 32: 859-868Google Scholar); both of are characteristic of a cancer cell that is a The same reported their to be In our study, we not directly the interaction IGFBP2 and integrin α5 was by Our in glioma are of was found in sarcoma, although our study, using a that the interaction IGFBP2 and integrin α5 is specific and mediated through the RGD In down the expression of integrin α5, we that the migration rates of IGFBP2-overexpressing cells were the that IGFBP2 to interact with integrin α5 to cell In the we also observed a in cell migration with integrin α5 Although the observed be it does to the as that the small of IGFBP2 and integrin α5 expression in SNB19 cells are indeed and contribute to cell mobility. In the present study further the role of IGFBP2 in glioma does IGFBP2 cell invasion by the extracellular matrix digestive it also promotes cell mobility through an which is known to be activated in We of for the We for