Regulation Of Integrin Expression Research Articles

Comprehensive Characterization of the Integrin Family Across 32 Cancer Types.

Integrin genes are widely involved in tumorigenesis. Yet, a comprehensive characterization of integrin family members and their interactome at the pan-cancer level is lacking. Here, we systematically analyzed integrin family in approximately 10,000 tumors across 32 cancer types. Globally, integrins represent a frequently altered and misexpressed pathway, with alteration and dysregulation overall being protumorigenic. Expression dysregulation, better than mutational landscape, of integrin family successfully identifies a subgroup of aggressive tumors with a high level of proliferation and stemness. The results reveal that several molecular mechanisms collectively regulate integrin expression in a context-dependent manner. For potential clinical usage, we constructed a weighted scoring system, integrinScore, to measure integrin signaling patterns in individual tumors. Remarkably, integrinScore was consistently correlated with predefined molecular subtypes in multiple cancers, with integrinScore-high tumors being more aggressive. Importantly, integrinScore was cancer-dependent and closely associated with proliferation, stemness, tumor microenvironment, metastasis, and immune signatures. IntegrinScore also predicted patients' response to immunotherapy. By mining drug databases, we unraveled an array of compounds that may modulate integrin signaling. Finally, we built a user-friendly database, Pan-cancer Integrin Explorer (PIExplorer; http://computationalbiology.cn/PIExplorer), to facilitate researchers to explore integrin-related knowledge. Collectively, we provide a comprehensive characterization of integrins across cancers and offer gene-specific and cancer-specific rationales for developing integrin-targeted therapy.

MicroRNAs Can Influence Ovarian Cancer Progression by Dysregulating Integrin Activity.

Ovarian cancer is a deadly disease that affects thousands of women worldwide. Integrins, transmembrane receptors that mediate cell adhesion and signaling, play important roles in ovarian cancer progression, metastasis, and drug resistance. Dysregulated expression of integrins is implicated in various cellular processes, such as cell migration, invasion, and proliferation. Emerging evidence suggests that microRNAs (miRNAs) can regulate integrin expression and function, thus affecting various physiological and pathological processes, including ovarian cancer. In this article, we review the current understanding of integrin-mediated cellular processes in ovarian cancer and the roles of miRNAs in regulating integrins. We also discuss the therapeutic potential of targeting miRNAs that regulate integrins for the treatment of ovarian cancer. Targeting miRNAs that regulate integrins or downstream signaling pathways of integrins may provide novel therapeutic strategies for inhibiting integrin-mediated ovarian cancer progression.

The human ion channel TRPM2 modulates migration and invasion in neuroblastoma through regulation of integrin expression

Transient receptor potential channel TRPM2 is highly expressed in many cancers and involved in regulation of key physiological processes including mitochondrial function, bioenergetics, and oxidative stress. In Stage 4 non-MYCN amplified neuroblastoma patients, high TRPM2 expression is associated with worse outcome. Here, neuroblastoma cells with high TRPM2 expression demonstrated increased migration and invasion capability. RNA sequencing, RT-qPCR, and Western blotting demonstrated that the mechanism involved significantly greater expression of integrins α1, αv, β1, and β5 in cells with high TRPM2 expression. Transcription factors HIF-1α, E2F1, and FOXM1, which bind promoter/enhancer regions of these integrins, were increased in cells with high TRPM2 expression. Subcellular fractionation confirmed high levels of α1, αv, and β1 membrane localization and co-immunoprecipitation confirmed the presence of α1β1, αvβ1, and αvβ5 complexes. Inhibitors of α1β1, αvβ1, and αvβ5 complexes significantly reduced migration and invasion in cells highly expressing TRPM2, confirming their functional role. Increased pAktSer473 and pERKThr202/Tyr204, which promote migration through mechanisms including integrin activation, were found in cells highly expressing TRPM2. TRPM2 promotes migration and invasion in neuroblastoma cells with high TRPM2 expression through modulation of integrins together with enhancing cell survival, negatively affecting patient outcome and providing rationale for TRPM2 inhibition in anti-neoplastic therapy.

High mobility group nucleosomal binding 2 reduces integrin α5/β1‐mediated adhesion of Klebsiella pneumoniae on human pulmonary epithelial cells via nuclear factor I

It has been reported that high mobility group nucleosomal binding domain 2 (HMGN2) is a nucleus-related protein that regulates gene transcription and plays a critical role in bacterial clearance. An elevated level of HMGN2 reduced integrin α5/β1 expression of human pulmonary epithelial A549 cells was demonstrated during Klebsiella pneumoniae infection, thus weakening bacterial adhesion and invasion. However, the mechanism by which HMGN2 regulates integrin expression remains unclear. This study found that a transcription factor-nuclear factor I (NFI), which serves as the potential target of HMGN2 regulated integrin expression. The results showed that HMGN2 was able to promote NFIA and NFIB expression by increasing H3K27 acetylation of NFIA/B promoter regions. The integrin α5/β1 expression was significantly enhanced by knockdown of NFIA/B via a siRNA approach. Meanwhile, NFIA/B silence could also compromise the inhibition effect of HMGN2 on the integrin α5/β1 expression. Mechanistically, it was demonstrated that HMGN2 facilitated the recruitment of NFI on the promoter regions of integrin α5/β1 according to the chromatin immunoprecipitation assay. In addition, it was further demonstrated that the knockdown of NFIA/B induced more adhesion of Klebsiella pneumoniae on pulmonary epithelial A549 cells, which could be reversed by the application of an integrin inhibitor RGD. The results revealed a regulatory role of HMGN2 on the transcription level of integrin α5/β1, indicating a potential treatment strategy against Klebsiella pneumoniae-induced infectious lung diseases.

Abstract C131: The SALL2 transcription factor promotes cell migration and focal adhesion turnover via regulation of integrin expression

Abstract SALL2 is a transcription factor, member of the Spalt gene family, which has been associated with development, differentiation and cancer. Interestingly, SALL2 deficiency leads to failure of both closure of the optic fissure and neurite outgrowth, suggesting a positive role for SALL2 in cell migration. Conversely, recent studies in ovarian cancer cells suggest that SALL2 plays a negative role in cell migration. Cell migration is a multistep process that involves cellular polarization, formation of membranous protrusions, assembly and disassembly of focal adhesions and cell traction. Hence, understanding the role of SALL2 in cell migration will be relevant to comprehend its function in physiology and disease. Here, we evaluated the role of SALL2 in cell migration, by using immortalized Sall2 knockout (KO) and Sall2 wild type Mouse Embryonic Fibroblasts (MEFs), and gain/loss of function experiments. To this end, we measured the effects of SALL2 in different aspects of cell migration, including wound healing in monolayers, cell adhesion, cell detachment, focal adhesion dynamics, as well as by immunofluorescence assays. For mechanistic insights we used Western blot, real time PCR, luciferase reporter assays, and bioinformatics analysis. Data were compared in unpaired Student’s t-tests by using the GraphPad Prism software. Our data indicate that SALL2 positively regulates cell migration by promoting cell polarization, cell detachment, and increased turnover of focal adhesions. Sall2-deficiency as well as Sall2 knockdown by short hairpin RNA led to reduced cell migration and focal adhesion dynamics. Accordingly, restored SALL2 expression through a TET-ON system in the Sall2 KO MEFs recovered cell migratory capabilities. Interestingly, SALL2 accelerated focal adhesion disassembly after nocodazole- wash out treatment. In addition, in a cell spreading context and after nocodazole treatment, SALL2 augmented Focal Adhesion Kinase (FAK) autophosphorylation on Y397 and promoted the expression of integrins b1 and a6. Taken together, our data suggest that SALL2 promotes MEF cell migration by modulating focal adhesion dynamics via a mechanism involving augmented expression of integrins b1 and a6. Since deregulation of cell migration promotes tumor formation, invasion and metastasis, our findings indicate that deregulation of SALL2 may be associated with the disease. Funded by FONDECYT 1191172, FONDECYT 1180495; FONDAP 15130011 Citation Format: Elizabeth Riffo, Mario Palma, Catalina Alarcon, Ariel Castro, Vicente Torres, Roxana Pincheira. The SALL2 transcription factor promotes cell migration and focal adhesion turnover via regulation of integrin expression [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C131. doi:10.1158/1535-7163.TARG-19-C131

Migrating cells control morphogenesis of substratum serving as track to promote directional movement of the collective.

In Drosophila embryos, caudal visceral mesoderm (CVM) cells undergo bilateral migration along the trunk visceral mesoderm (TVM) in order to form midgut muscles. Mutation of FGF receptor Heartless (Htl) has been shown to cause CVM migration defects, particularly midline crossing of the bilateral groups. Here, we show that htl mutants also exhibit TVM defects including contralateral merging. Both CVM mismigration and TVM contralateral merging are attenuated by restoring FGF signaling specifically in the CVM, suggesting that migrating CVM cells influence TVM morphogenesis; however, the inverse, supplying FGF to the TVM, does not rescue CVM mismigration. In addition, we show that FGF regulates integrin expression in both tissues, but only providing a source of integrin specifically to the TVM attenuates the contralateral merging phenotype. Finally, we demonstrate that the CVM influences cell shape in the TVM, and a loss of CVM results in TVM morphological defects. In summary, this study provides insight into how a migrating collective of cells can influence their tissue substrate and supports the view that morphogenesis of tissues during development is interdependent.

Transforming growth factor β1 enhances adhesion of endometrial cells to mesothelium by regulating integrin expression.

Endometriosis is the abnormal growth of endometrial cells outside the uterus, causing pelvic pain and infertility. Furthermore, adhesion of endometrial tissue fragments to pelvic mesothelium is required for the initial step of endometriosis formation outside uterus. TGF-β1 and adhesion molecules importantly function for adhesion of endometrial tissue fragments to mesothelium outside uterus. However, the function of TGF-β1 on the regulation of adhesion molecule expression for adhesion of endometrial tissue fragments to mesothelium has not been fully elucidated. Interestingly, transforming growth factor β1 (TGF-β1) expression was higher in endome-triotic epithelial cells than in normal endometrial cells. The adhesion efficiency of endometriotic epithelial cells to meso-thelial cells was also higher than that of normal endometrial cells. Moreover, TGF-β1 directly induced the adhesion of endometrial cells to mesothelial cells through the regulation of integrin of αV, α6, β1, and β4 via the activation of the TGF-β1/TGF-βRI/Smad2 signaling pathway. Conversely, the adhesion of TGF-β1-stimulated endometrial cells to mesothelial cells was clearly reduced following treatment with neutralizing antibodies against specific TGF-β1-mediated integrins αV, β1, and β4 on the endometrial cell membrane. Taken together, these results suggest that TGF-β1 may act to promote the initiation of endometriosis by enhancing integrin-mediated cell-cell adhesion.

Nitric oxide increases the migratory activity of non-small cell lung cancer cells via AKT-mediated integrin αv and β1 upregulation.

Previously, nitric oxide (NO) has been found to affect the metastatic behavior of various types of cancer. In addition, it has been found that alterations in integrin expression may have profound effects on cancer cell survival and migration. Here, we aimed at assessing the effects of non-toxic concentrations of NO on human non-small cell lung cancer (NSCLC) cells, including the expression of integrins and the migration of these cells. The cytotoxic and proliferative effects of NO on human NSCLC-derived H460, H292 and H23 cells were tested by MTT assay. The migration capacities of these cells was evaluated by wound healing and transwell migration assays. The expression of integrins and migration-associated proteins was determined by Western blot analyses. We found that NO treatment caused a significant increase in the expression of integrin αv and β1 in all three NSCLC-derived cell lines tested. Known migration-associated proteins acting downstream of these integrins, including focal adhesion kinase (FAK), active RhoA (Rho-GTP) and active cell division control 42 (Cdc42-GTP), were found to be significantly activated in response to NO. In addition, we found that NO-treated cells showed an increased motility and that this motility was associated with a significant increase in the number of filopodia per cell. We also found that NO-treated cells exhibited increased active protein kinase G (PKG), protein kinase B (AKT) and FAK expression levels. Using a pharmacological approach, we found that the integrin-modulating effect of NO is most likely brought about by a PKG/AKT-dependent mechanism, since the observed changes in integrin expression were abolished by AKT inhibitors, but not by FAK inhibitors. Our data suggest a novel role of NO in the regulation of integrin expression and, concomitantly, the migratory capacity of NSCLC cells.

PHLPP negatively regulates cell motility through inhibition of Akt activity and integrin expression in pancreatic cancer cells.

Pancreatic adenocarcinoma is currently the fourth leading cause for cancer-related mortality. Malignant progression of pancreatic cancer depends not only on rapid proliferation of tumor cells but also on increased cell motility. In this study, we showed that increased PHLPP expression significantly reduced the rate of migration in pancreatic ductal adenocarcinoma (PDAC) cells whereas knockdown of PHLPP had the opposite effect. In addition, cell motility at the individual cell level was negatively regulated by PHLPP as determined using time-lapse imaging. Interestingly, the expression of β1 and β4 integrin proteins were decreased in PHLPP overexpressing cells and increased in PHLPP knockdown cells whereas the mRNA levels of integrin were not altered by changes in PHLPP expression. In determining the molecular mechanism underlying PHLPP-mediated regulation of integrin expression, we found that inhibition of lysosome activity rescued integrin expression in PHLPP overexpressing cells, thus suggesting that PHLPP negatively controls cell motility by inhibiting Akt activity to promote lysosome-dependent degradation of integrins. Functionally, the increased cell migration observed in PHLPP knockdown cells was effectively blocked by the neutralizing antibodies against β1 or β4 integrin. Taken together, our study identified a tumor suppressor role of PHLPP in suppressing cell motility by negatively regulating integrin expression in pancreatic cancer cells.

Abstract 2056: SIRT1 silencing suppresses prostate cancer growth and metastasis in an orthotopic prostate cancer mouse model

Abstract Tumor environment is critical for tumor growth and progression, and orthotopic mouse model allows accurately study tumor development in an appropriate tumor environment. SIRT1, a class III histone deacetylase, has been shown overexpressed in prostate cancer and is a biomarker for prostate cancer recurrence. Although these data have suggested the importance of the role SIRT1 plays in prostate cancer progression, the role of SIRT1 in tumor growth and progression within, specifically, a prostate tumor environment has not been established. In this study, we established an advanced prostate cancer PC3MM2 orthotopic mouse model to study the effects of SIRT1 silencing on prostate cancer growth and progression. Our data has shown that SIRT1 knockdown greatly suppresses tumor formation within a prostate tumor environment, along with an inhibition of metastasis to bone and liver. To further study the mechanism by which SIRT1 controls tumor growth and progression, we demonstrated that SIRT1 silencing reduces prostate cancer cell adhesion to cell matrix, and that this silencing also suppresses cancer cell growth and colony formation in a cell matrix dependent manner. Moreover, our data showed that SIRT1 regulates integrin expression and focal adhesion complex formation. Furthermore, we shows that SIRT1 silencing from prostate cancer cell significantly inhibited human umbilical vein endothelial cell (HUVEC) tube formation, suggests an important role of SIRT1 in prostate cancer angiogenesis. Thus, we have reported for the first time that SIRT1 plays a critical role in prostate cancer growth and progression using orthotopic mouse model, and demonstrated for the first time that SIRT1 regulates integrin expression, focal adhesion formation, tumor cell and matrix interaction, and angiogenesis. These results suggest SIRT1 regulates prostate cancer growth and progression through multiple mechanisms and that SIRT1 is a potential target in prostate cancer treatment. Citation Format: Yan Dai, Lijia Zhu, Elizabeth Cho, Audrey Hagiwara, Douglas Faller, Sun-Jin Kim, Isaiah J. Fidler, Marina Amaro. SIRT1 silencing suppresses prostate cancer growth and metastasis in an orthotopic prostate cancer mouse model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2056. doi:10.1158/1538-7445.AM2015-2056

Transcription factor hlh-2/E/Daughterless drives expression of α integrin ina-1 during DTC migration in C. elegans

Integrins are involved in a vast number of cell behaviors due to their roles in adhesion and signaling. The regulation of integrin expression is of particular interest as a mechanism to drive developmental events and for the role of altered integrin expression profiles in cancer. Dynamic regulation of the expression of integrin receptors is required for the migration of the distal tip cell (DTC) during gonadogenesis in Caenorhabditis elegans. α integrin ina-1 is required for DTC motility, yet is up-regulated by an unknown mechanism. Analysis of the promoter for α integrin ina-1 identified two E-box sequences that are required for ina-1 expression in the DTC. Knockdown of transcription factor hlh-2, an established E-box binding partner and ortholog of E/Daughterless, prevented expression of a transcriptional fusion of the ina-1 promoter to RFP and blocked DTC migration. Similarly, knockdown of hlh-2 also prevented expression of a translational fusion of the genomic ina-1 gene to GFP while blocking DTC migration. Knockdown of HLH-2 binding partner MIG-24 also reduced ina-1 expression and DTC migration. Overall, these results show that the transcription factor hlh-2 is required for up-regulation of ina-1 at the onset of DTC migration.

Integrins Regulate Apical Constriction via Microtubule Stabilization in the Drosophila Eye Disc Epithelium

During morphogenesis, extracellular signals trigger actomyosin contractility in subpopulations of cells to coordinate changes in cell shape. To illuminate the link between signaling-mediated tissue patterning and cytoskeletal remodeling, we study the progression of the morphogenetic furrow (MF), the wave of apical constriction that traverses the Drosophila eye imaginal disc preceding photoreceptor neurogenesis. Apical constriction depends on actomyosin contractility downstream of the Hedgehog (Hh) and bone morphogenetic protein (BMP) pathways. We identify a role for integrin adhesion receptors in MF progression. We show that Hh and BMP regulate integrin expression, the loss of which disrupts apical constriction and slows furrow progression; conversely, elevated integrins accelerate furrow progression. We present evidence that integrins regulate MF progression by promoting microtubule stabilization, since reducing microtubule stability rescues integrin-mediated furrow acceleration. Thus, integrins act as a genetic link between tissue-level signaling events and morphological change at the cellular level, leading to morphogenesis and neurogenesis in the eye.

The Roles of MAPKs in Rabbit Nucleus Pulposus Cell Apoptosis Induced by High Osmolality

Earlier work has suggested that the p38 MAPK, JNK1/2 and ERK1/2 signal pathway existed in nucleus pulposus cells and the cell growth, differentiation and apoptosis were regulated by them. Because osmotic fluctuations are inevitable in the physicochemical environment of intervertebral disc cells, high osmolality could activate p38 MAPK, JNK1/2 and ERK1/2 signal pathway. The effects of high osmolality on the catabolic program and proliferation of nucleus pulposus cells are still not clear. To explore the possible roles of MAPKs in rabbit nucleus pulposus cell apoptosis induced by high osmolality. Rabbit nucleus pulposus cells were cultured and divided into different group at random. The cells were pretreated with inhibitor for p38 MAPK, JNK1/2 and ERK1/2 signal pathway respectively. In next step, the cells were cultured in different osmolality environment for different time at 37°C in 5% carbon dioxide incubator. After treatments, ratio of apoptosis was measured by flow cytometry, and western blotting was performed to quantify the expression of the activated forms of p38 MAPK, JNK1/2 and ERK1/2. Furthermore, immunofluorescence analysis with confocal microscopy was performed to confirm the hyperosmolality effects on activation of p38 MAPK, JNK1/2 and ERK1/2 signal pathways in nucleus pulposus cells. Our results show that in 500 and 600 mOsm/kg medium, rabbit nucleus pulposus cell apoptosis increased, and a persistent phosphorylation of p38 MAPK, JNK1/2 and ERK1/2 proteins were observed. In the same condition, the apoptotic cells death remarkably decreased when the p38 MAPK and JNK1/2 signal pathways were blocked by their inhibitors SB203580, SP600125 repectively. On the other side, the apoptotic cells death rate reraised greatly when the ERK1/2 signal pathways were blocked by its inhibitor PD98059. High osmolality activated p38MAPK, JNK1/2 and ERK1/2 in rabbit nucleus pulposus cell, and the activated p38 MAPK and JNK1/2 induced cell apoptosis, on the contrary, the activated ERK1/2 made the cell survived.

Rab25 regulates integrin expression in polarized colonic epithelial cells.

Rab25 is a tumor suppressor for colon cancer in humans and mice. To identify elements of intestinal polarity regulated by Rab25, we developed Caco2-BBE cell lines stably expressing short hairpin RNA for Rab25 and lines rescuing Rab25 knockdown with reexpression of rabbit Rab25. Rab25 knockdown decreased α2-, α5-, and β1-integrin expression. We observed colocalization and direct association of Rab25 with α5β1-integrins. Rab25 knockdown also up-regulated claudin-1 expression, increased transepithelial resistance, and increased invasive behavior. Rab25-knockdown cells showed disorganized brush border microvilli with decreases in villin expression. All of these changes were reversed by reintroduction of rabbit Rab25. Rab25 knockdown altered the expression of 29 gene transcripts, including the loss of α5-integrin transcripts. Rab25 loss decreased expression of one transcription factor, ETV4, and overexpression of ETV4 in Rab25-knockdown cells reversed losses of α5β1-integrin. The results suggest that Rab25 controls intestinal cell polarity through the regulation of gene expression.

Protein kinase B (PKB/c-akt) regulates homing of hematopoietic progenitors through modulation of their adhesive and migratory properties

AbstractLimited number of hematopoietic stem cells in umbilical cord blood (UCB) presents a problem when using UCB for stem cell transplantation. Improving their homing capacity could reduce the need for high initial cell numbers during transplantation procedures. Although it is evident that protein kinase B (PKB/c-Akt) plays an important role in regulation of migration of various cell types, a role for PKB in regulation of migration and homing of human hematopoietic stem and progenitor cells remains to be determined. PKB activity was found to be required for induction of adhesion to bone marrow–derived stromal cells and detrimental for migration of UCB-derived CD34+ hematopoietic progenitors. In addition, PKB activity was found to positively regulate integrin expression. CD34+ hematopoietic progenitors, and their capacity to form colonies in vitro, were not affected by transient inhibition of PKB. Finally, transplantation of β2-microglobulin−/− nonobese diabetic/severe combined immunodeficient mice with CD34+ cells ectopically expressing constitutively active PKB resulted in reduced migration to the bone marrow, whereas inhibition of PKB activity resulted in an induction in bone marrow homing and engraftment. These results indicate that transient inhibition of PKB activity may provide a means for ex vivo stem cell manipulation to improve bone marrow transplantation regimes.

Integrin expression and function in the response of primary culture hepatic stellate cells to connective tissue growth factor (CCN2)

Production of connective tissue growth factor (CCN2, also known as CTGF) is a hallmark of hepatic fibrosis. This study examined early primary cultures of hepatic stellate cells (HSC) for (i) CCN2 regulation of its cognate receptor integrin subunits; and (ii) interactions between CCN2 and integrin α5β1, heparan sulphate proteoglycans (HSPG) or fibronectin (FN) in supporting cell adhesion. HSC were isolated from healthy male Balb/c mice. mRNA levels of CCN2 or α5, β1, αv or β3 integrin subunits were measured in days 1–7 primary culture HSC, and day 3 or day 7 cells treated with recombinant CCN2 or CCN2 small interfering RNA. Interactions between CCN2 and integrin α5β1, HSPG or FN were investigated using an in vitro cell adhesion assay. Co-incident with autonomous activation over the first 7 days, primary culture HSC increasingly expressed mRNA for CCN2 or integrin subunits. Addition of exogenous CCN2 or knockdown of endogenous CCN2 differentially regulated integrin gene expression in day 3 versus day 7 cells. Either full length CCN2 (‘CCN21–4’) or residues 247–349 containing module 4 alone (‘CCN24’) supported day 3 cell adhesion in an integrin α5β1- and HSPG-dependent fashion. Adhesion of day 3 cells to FN was promoted in an integrin α5β1-dependent manner by CCN21–4 or CCN24, whereas FN promoted HSPG-dependent HSC adhesion to CCN21–4 or CCN24. These findings suggest CCN2 regulates integrin expression in primary culture HSC and supports HSC adhesion via its binding of cell surface integrin α5β1, a novel CCN2 receptor in primary culture HSC which interacts co-operatively with HSPG or FN.

SRC-1 Promotes Breast Cancer Metastasis by Activating MAPK Pathway.

Abstract Background: Steroid receptor coactivator (SRC-1) was defined as a nuclear receptor coactivator. It interacts with nuclear receptor and other transcriptional factors and promotes target genes expression. In breast cancer, SRC-1 expression correlates positively with HER2 expression, disease recurrence and resistance to endocrine therapy. Our previous work demonstrated that knockout of SRC-1 in mice suppressed breast cancer metastasis without affecting primary tumor initiation and growth in the MMTV-PyMT transgenic mice. However, the molecular mechanism responsible for SRC-1 in breast cancer metastasis is still unclear.Material and Methods: To further study the function of SRC-1 in breast cancer metastasis, we generated transgenic mice with overexpression of human SRC-1 in the mouse mammary epithelial cells. The mammary glands of these mice exhibited normal development. After crossing these mice with MMTV-TVA (avian subgroup A receptor gene, TVA) transgenic mice, we obtained MMTV-TVA/MMTV-hSRC-1 (tester) and MMTV-TVA/WT (control) biogenic mice. RCAS (avian leukosis virus) viruses, which contain MMTV-PyMT expression cassette and can bind to TVA, were injected into mammary gland to induce mammary tumor. Tumor initiation, growth and metastasis were carefully examined with these mice. To investigate mechanism, multiple PyMT tumor cell lines were generated form individual primary tumor with or without SRC-1 and cell migration and invasion were compared with those cells and human breast cancer cells.Results and discuss: No difference in tumor initiation and growth was observed in those mice, but metastasis incidence of breast cancer to lung increased significantly in PyMT/TVA/hSRC-1 mice compared with PyMT/TVA/WT control mice. Tumor metastasis in lung also presented higher index in PyMT/TVA/hSRC-1 mice. In vitro study with PyMT/SRC-1 WT and KO cell lines showed SRC-1 deficiency disturbed cells migration and invasion. WT tumor cells adhered faster to extracellular matrix fibronecetin (FN) and presented high levels of phosphorylated forms of FAK, c-Src, Erk, Jnk and activated Rac1. Western blotting and real-time RT-PCR revealed lower integrin alpha5 and Gem, one of GTP binding protein, levels in SRC-1 deficient tumor cells. In human breast cancer MDA-MB-231 cells, SRC-1 knockdown led to decreased cell migration and invasion. Therefore, SRC-1 may regulate integrin expression and MAPK pathway to promote cancer cell migration and metastasis. Our study provides a possibility to inhibit breast cancer metastasis by targeting SRC-1 function. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6150.

Acheron, a Lupus antigen family member, regulates integrin expression, adhesion, and motility in differentiating myoblasts

Acheron (Achn) was originally identified as novel gene that is induced when insect muscles become committed to die at the end of metamorphosis. In separate studies, we have demonstrated that Achn acts upstream of MyoD and is required by mammalian myoblasts to either differentiate or undergo apoptosis following loss of growth factors. In the present study we examined the role of Achn in regulating integrin-extracellular matrix interactions that are required for myogenesis. Both control C2C12 myoblasts and those engineered to express ectopic Achn expressed the fibronectin receptor integrin alpha(5)beta(1) in the presence of growth factors and the laminin receptor alpha(7)beta(1) following growth factor withdrawal. Expression of the laminin receptor was blocked in cells expressing either Achn antisense or an Achn deletion mutant that blocks differentiation. Control cells and those expressing ectopic Achn undergo sequential and transient increases in both substrate adhesion and migration before cell fusion. Blockade of Achn expression reduced these effects on laminin but not on fibronectin. Taken together, these data suggest that Achn may influence differentiation in part via its control of cell adhesion dynamics.

CCN3/Nephroblastoma Overexpressed Matricellular Protein Regulates Integrin Expression, Adhesion, and Dissemination in Melanoma

CCN3/nephroblastoma overexpressed belongs to the CCN family of genes that encode secreted proteins associated with the extracellular matrix (ECM) and exert regulatory effects at the cellular level. Overexpression of CCN3 was shown in metastatic melanoma cells compared with cells of the primary tumor from the same patient. Analysis of short-term cultures from 50 primary and metastatic melanomas revealed a heterogeneous expression pattern of both the 46-kDa full-length cytoplasmic/secreted protein and the 32-kDa nuclear-truncated form. The different protein expression patterns were not associated with gene alterations or polymorphisms. Like the metastatic cells expressing high levels of the 46-kDa CCN3, cells transfected to overexpress CCN3 showed increased adhesion to ECM proteins, whereas inhibition of CCN3 expression by small interfering RNA decreased adhesion to laminin and vitronectin. CCN3 overexpression induced increased expression of laminin and vitronectin integrin receptors alpha 7 beta 1 and alpha v beta 5 by increasing their mRNA production. Moreover, CCN3 secreted by melanoma cells acted as an adhesion matrix protein for melanoma cells themselves. Analysis of CCN3 protein expression with respect to melanoma progression detected the protein in all visceral metastases tested and in most nodal metastases from relapsing patients but in only a few nodal metastases from nonrelapsing patients and cutaneous metastases. Consistently, xenotransplantation in immunodeficient mice showed a higher metastatic potential of melanoma cells overexpressing CCN3. Together, these data indicate a role for CCN3 in melanoma cell interaction with the ECM by regulating integrin expression, resulting in altered cell adhesion and leading melanoma progression to aggressive disease.

Pentoxifylline modulates cell surface integrin expression and integrin mediated adhesion of B16F10 cells to extracellular matrix components

Our previous studies demonstrated that Pentoxifylline (PTX), a phosphodiesterase inhibitor could inhibit the lung homing of B16-F10 melanoma cells in C57BL/6 mice. In this study we have looked at the effect of PTX on cell surface integrin expression and integrin mediated adhesion of B16-F10 melanoma cells. B16F10 cells treated with PTX when injected through the tail vein of mice showed a 75% reduction in pulmonary nodules as compared to control untreated cells. PTX brought about a significant reduction in the integrin mediated adhesion of F10 cells to Fibronectin and Vitronectin (58.75% + 3.4 S.E and 60% + 1.7 S.E respectively if control was considered as 100 %). This inhibition in adhesion was evident upto 4 hours only and treatment for 24 hours brought about an increase in adhesion (135.5 % + 0.5 S.E). Flow cytometric analysis showed higher surface expressions of αv, α5 and αIIb integrin subunits in B16-F10 as compared to the low metastatic cell line B16-F1 suggesting a role for these integrins in determining the metastatic potential. PTX brought about a significant decrease in the cell surface expression of α5, αIIb and β1integrin subunits but not that of the αv subunit on B16-F10 cells. PTX also brought about a reduction in the total cellular protein levels of β1 and αv integrin subunits. Various isoforms of Protein Kinase C (PKC) has been shown to regulate integrin expression, localization and activity. Hence we looked at the effect of PTX on total cellular PKC activity. PTX brought about a significant reduction in total cellular PKC activity (82.66 + 0.593). Collectively our results indicate that the antimetastatic action of PTX is mediated, at least in part through its effects on adhesion and the surface expression of specific integrin receptors.