Direct integrin alphavbeta6-ERK binding: implications for tumour growth

Blockade of the mitogen-activated protein (MAP) kinase pathway suppresses growth of colon cancer in vivo. Here we demonstrate a direct link between the extracellular signal-regulated kinase ERK2 and the growth-promoting cell adhesion molecule, integrin alphavbeta6, in colon cancer cells. Down-regulation of beta6 integrin subunit expression inhibits tumour growth in vivo and MAP kinase activity in response to serum stimulation. In alphavbeta6-expressing cells ERK2 is bound only to the beta6 subunit. The increase in cytosolic MAP kinase activity upon epidermal growth factor stimulation is all accounted for by beta6-bound ERK. Deletion of the ERK2 binding site on the beta6 cytoplasmic domain inhibits tumour growth and leads to an association between ERK and the beta5 subunit. The physical interaction between integrin alphavbeta6 and ERK2 defines a novel paradigm of integrin-mediated signalling and provides a therapeutic target for cancer treatment.     

A peptide selected by biopanning identifies the integrin alphavbeta6 as a prognostic biomarker for nonsmall cell lung cancer

The development of new modes of diagnosis and targeted therapy for lung cancer is dependent on the identification of unique cell surface features on cancer cells and isolation of reagents that bind with high affinity and specificity to these biomarkers. We recently isolated a 20-mer peptide which binds to the lung adenocarcinoma cell line, H2009, from a phage-displayed peptide library. We show here that the cellular receptor for this peptide, TP H2009.1, is the uniquely expressed integrin, alphavbeta6, and the peptide binding to lung cancer cell lines correlates to integrin expression. The peptide is able to mediate cell-specific uptake of a fluorescent nanoparticle via this receptor. Expression of alphavbeta6 was assessed on 311 human lung cancer samples. The expression of this integrin is widespread in early-stage nonsmall cell lung carcinoma (NSCLC). Log-rank test and Cox regression analyses show that expression of this integrin is significantly associated with poor patient outcome. Preferential expression is observed in the tumors compared with the surrounding normal lung tissue. Our data indicate that alphavbeta6 is a prognostic biomarker for NSCLC and may serve as a receptor for targeted therapies. Thus, cell-specific peptides isolated from phage biopanning can be used for the discovery of cell surface biomarkers, emphasizing the utility of peptide libraries to probe the surface of a cell.     

Role of alphavbeta3 integrin receptors in breast tumor

The intriguing problem of tumor metastasis involves adhesion of the metastatic cells via the integrin group of cell surface receptors to the ECM proteins of the basement membrane. Modulation of integrin family of cell surface receptors is believed to be associated with stages of tumor metastasis. In this present study, results obtained indicate that alphavbeta3 vitronectin receptors may play an important role in the malignant behaviour of human breast tumor. Alphavbeta3 integrin receptors can modulate the activity of collagenase enzyme and thereby the invasive property of breast tumor cells.     

A negative role of SHP-2 tyrosine phosphatase in growth factor-dependent hematopoietic cell survival

SHP-2 tyrosine phosphatase is highly expressed in hematopoietic cells; however, the function of SHP-2 in hematopoietic cell processes is not fully understood. Recent identification of SHP-2 mutations in childhood leukemia further emphasizes the importance of SHP-2 regulation in hematopoietic cells. We previously reported that SHP-2 played a positive role in IL-3-induced activation of Jak2 kinase in a catalytic-dependent manner. Interestingly, enforced expression of wild-type (WT) SHP-2 in Ba/F3 cells enhanced growth factor deprivation-induced apoptosis. Biochemical analyses revealed that although IL-3 activation of Jak2 kinase was increased, tyrosyl phosphorylation of its downstream substrate STAT5 was disproportionately decreased by the overexpression of SHP-2. Following IL-3 deprivation, the tyrosyl phosphorylation of STAT5 that is required for its antiapoptotic activity was rapidly diminished in SHP-2 overexpressing cells. As a result, reduction of the putative downstream targets of STAT5-Bcl-X(L) and pim-1 was accelerated by overexpression of SHP-2. Further investigation showed that SHP-2 associated with STAT5, and that it was indeed able to dephosphorylate STAT5. Finally, overexpression of SHP-2 in primary bone marrow hematopoietic progenitor cells compromised their differentiative and proliferative potential, and enhanced growth factor withdrawal-induced cell death. And, the effect of SHP-2 overexpression on growth factor-dependent survival was diminished in STAT5-deficient hematopoietic cells. Taken together, these results suggest that SHP-2 tyrosine phosphatase negatively regulates hematopoietic cell survival by dephosphorylation of STAT5.     

Rare mutations of the growth suppressor genes involved in negative regulation of the cell cycle

The growth suppressing activity of the retinoblastoma susceptibility gene product, pRb, is down regulated by cyclin-dependent kinases 4 and 6 (CDK4 and CDK6) whose activity is negatively regulated by CDK inhibitors of the p16 family. We have previously reported point mutations of the p16/CDKN2 gene in 4 (57%) of 7 oral squamous cell carcinoma (SCC) cell lines. In the current study, we examined the mutational status of CDK inhibitors, including 3 genes of the p16 family (p16, p15 and p18), in 50 human oral SCCs, and also additional results concerning their loss of heterozygosity in the regions of the p16, p15 and p18 genes. Our results demonstrated that 2 of 50 (4%) primary oral SCCs had nonsense mutations of the p16 gene, and 2 of 50 (4%) showed frameshift mutations of the p18 gene. However, we detected no mutation of the p15 gene in any of the 50 oral SCCs. In addition, no evidence of hypermethylation of the p16 gene was found in our series. To better understand the extent of alterations affecting chromosomes 9p21 (location of the p15/p16 genes) and 1p32 (location of the p18 gene), loss of heterozysity (LOH) on these locations was examined. LOH was detected in 16 of 34 (47%) informative samples that had no detectable mutation of the p15/p16 genes on 9p21, but we found no LOH at 1p32. These results strongly suggest that a putative tumor suppressor gene for oral SCC may be present on chromosome 9p21-22, while the p16, p15 and p18 genes play a minor role in the oncogenesis of this cancer.     

Oesophageal squamous cell carcinoma in high-risk Chinese populations: Possible role for vascular epithelial growth factor A

BackgroundMechanisms involved in wound healing play some role in carcinogenesis in multiple organs, likely by creating a chronic inflammatory milieu. This study sought to assess the role of genetic markers in selected inflammation-related genes involved in wound healing (interleukin (IL)-1a, IL-1b, IL-1 Receptor type I (IL-1Ra), IL-1 Receptor type II (IL-1Rb), tumour necrosis factor (TNF)-α, tumour necrosis factor receptor superfamily member (TNFRSF)1A, nuclear factor kappa beta (NF-kB)1, NF-kB2, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, hypoxia induced factor (HIF)-1α, vascular endothelial growth factor (VEGF)A and P-53) in risk to oesophageal squamous cell carcinoma (OSCC).MethodsWe genotyped 125 tag single nucleotide polymorphism (SNP)s in 410 cases and 377 age and sex matched disease-free individuals from Nutritional Intervention Trial (NIT) cohort, and 546 cases and 556 controls individually matched for age, sex and neighbourhood from Shanxi case–control study, both conducted in high-risk areas of north-central China (1985–2007). Cox proportional-hazard models and conditional logistic regression models were used for SNPs analyses for NIT and Shanxi, respectively. Fisher’s inverse test statistics were used to obtain gene-level significance.ResultsMultiple SNPs were significantly associated with OSCC in both studies, however, none retained their significance after a conservative Bonferroni adjustment. Empiric p-values for tag SNPs in VEGFA in NIT were highly concentrated in the lower tail of the distribution, suggesting this gene may be influencing risk. Permutation tests confirmed the significance of this pattern. At the gene level, VEGFA yielded an empiric significance (P = 0.027) in NIT. We also observed some evidence for interaction between environmental factors and some VEGFA tag SNPs.ConclusionOur finding adds further evidence for a potential role for markers in the VEGFA gene in the development and progression of early precancerous lesions of oesophagus.     

跨膜接头蛋白CBP对皮肤鳞癌细胞A431生长增殖的负调控作用研究

背景与目的：跨膜接头蛋白(Csk-binding protein,CBP)是新发现的Src家族成员,与多种肿瘤的发生有关。该研究旨在观察CBP基因过表达对皮肤鳞癌细胞系A431增殖及细胞凋亡的影响,探讨其相关的分子机制。方法：构建CBP-增强型绿色荧光蛋白(enhanced green fluorescent protein,EGFP)融合蛋白的慢病毒过表达载体,采用反转录病毒转染的方法建立CBP过表达的A431细胞株。实验分为亲本细胞组(未进行基因转染的A431细胞)、对照组(A431细胞转染仅含EGFP阴性对照病毒)和实验组(A431细胞转染CBP-EGFP病毒)。在激光共聚焦显微镜下观察细胞转染率,验证转染成功与否;CCK-8法检测CBP过表达对A431细胞增殖能力的影响,并采用流式细胞术(flow cytometry,FCM)检测对细胞凋亡的影响;实时荧光定量聚合酶链反应(real-time fluorescence quantitative polymerase chain reaction,RTFQ-PCR)和蛋白［质］印迹法(Western blot)检测Lck、Csk和Fyn三种上游信号转导分子分别在mRNA和蛋白中的表达水平变化。结果：建立了稳定过表达CBP的A431细胞株;CCK-8法结果提示,CBP过表达明显抑制细胞生长,第2~6天的组间差异有统计学意义(P<0.05);FCM检测显示,实验组细胞凋亡率显著增加,与亲本细胞组及对照组相比差异有统计学意义(P<0.001);RTFQ-PCR结果显示,实验组A431细胞Lck mRNA的相对表达水平显著下调(P<0.001),实验组细胞Csk和Fyn mRNA的表达分别约为亲本细胞组的1.6倍和3.8倍,表达显著上调(P<0.001);Western blot结果表明,实验组Lck蛋白的相对表达水平明显下降(P<0.001),实验组细胞Csk和Fyn蛋白与亲本细胞组和对照组相比表达明显增加(P<0.001)。结论：CBP过表达可抑制皮肤鳞癌细胞增殖,诱导细胞凋亡及坏死。CBP通过调节上游信号转导通路中的蛋白酪氨酸激酶Lck、Csk和Fyn来调控细胞的增殖活性。     

The role of metabolism in mammary epithelial cell growth inhibition by the isoflavones genistein and biochanin A

The basis for the differential sensitivity of cultured normalhuman mammary epithelial (HME) cells and a transformed humanbreast cancer MCF-7 cell line to growth inhibition by the isoflavonegenistein and its 4'-methyl ether derivative, biochanin A, wasexamined. In HME cells genistein is 5-fold more potent as agrowth inhibitor than biochanin A, whereas in MCF-7 cells biochaninA and genistein are equally potent as growth inhibitors. Basedon its properties as an in vitro protein tyrosine kinase (PTK)inhibitor, biochanin A would be expected to be a less potentgrowth inhibitor than genistein. To determine whether isoflavonemetabolism could account for the observed differences in growthinhibition, metabolism experiments were conducted with HME andMCF-7 cells using [4-¹⁴C]genistein and [4-¹⁴C]biochanin A. MCF-7cells extensively metabolized both isoflavones, producing twogenistein metabolites with molecular weights of 350 and 380and three biochanin A metabolites with molecular weights of270, 350 and 380. In contrast, significant genistein or biochaninA metabolism was not observed in HME cells. Using mass spectrometryand nuclear magnetic resonance analysis, metabolite 350 fromgenistein and biochanin A experiments was identified as genistein7-sulfate; biochanin A metabolite 270 was identified as genistein.Metabolite 380 was not unequivocally identified, but appearedto be a hydroxylated and methylated form of genistein sulfate.In MCF-7 cells, genistein 7-sulfate and metabolite 380 weredetected primarily in the cell media fraction, suggesting thatonce formed these polar metabolites were excreted from the cells.These data show that isoflavone metabolism by transformed breastepithelial cells modulates the growth inhibitory effects ofgenistein and biochanin A. In MCF-7 cells, genistein metabolismwas correlated with a decrease in growth inhibition, whereasbiochanin A metabolism was associated with an increase in growthinhibition.     

Expression profiling reveals genes associated with transendothelial migration of tumor cells: a functional role for alphavbeta3 integrin

Transendothelial migration is a key step in the extravasation of tumor cells during metastasis formation. Here, we have classified 45 human tumor cell lines derived from various tissues according to their capacity for transendothelial migration in vitro. We could distinguish cell lines showing strong transmigration (TEM+ cell lines) from others that did not transmigrate (TEM- cell lines). By DNA microarray analysis we could cluster TEM+ and TEM- cell lines according to their gene expression pattern and identify genes differentially expressed between the 2 groups. Among these we found the integrin beta3 subunit to be highly expressed in TEM+ cell lines as compared to TEM- cell lines. Cell surface localization of alphavbeta3 integrin receptors was exclusively found in TEM+ cell lines. Transendothelial migration of TEM+ cells but not their adhesion to the endothelial cells, or invasion into collagen gels could be blocked with an antibody against alphavbeta3 integrin and by RNAi mediated knock-down of the integrin beta3 subunit. These data establishes alphavbeta3 integrin as one key component of the transendothelial migration process of tumor cells, and as a potential target for anti-metastatic therapy. Our gene expression analysis of a defined collection of tumor cell lines can be used as a starting point to identify further genes functionally involved in transendothelial migration.     

Abrogation of the interaction between osteopontin and alphavbeta3 integrin reduces tumor growth of human lung cancer cells in mice

Osteopontin (OPN) is a multifunctional cytokine involved in cell signaling by interacting with alphavbeta3 integrins. Recent clinical studies have indicated that OPN expression is associated with tumor progression and poor prognosis among patients with lung cancer. However, the biological role of OPN in human lung cancer has not yet been well-defined. The purpose of this study is to investigate and provide evidence for the causal role of OPN regarding tumor growth and angiogenesis in human lung cancer. In this study, we developed a stable OPN transfectant from human lung cancer cell line SBC-3 which does not express the intrinsic OPN mRNA. To reveal the in vivo effect of OPN on tumor growth of human lung cancer, we subcutaneously injected OPN-overexpressing SBC-3 cells (SBC-3/OPN) and control cells (SBC-3/NEO) into the nude mice. Transfection with the OPN gene significantly increased in vivo tumor growth and neovascularization of SBC-3 cells in mice. These in vivo effects of OPN were markedly suppressed with administration of anti-alphavbeta3 integrin monoclonal antibody or anti-angiogenic agent, TNP-470. Furthermore, recombinant OPN protein enhanced human umbilical vein endothelial cell (HUVEC) proliferation in vitro, and this enhancement was significantly inhibited with the addition of anti-alphavbeta3 integrin antibody. Taken together, these results suggest that OPN plays a crucial role for tumor growth and angiogenesis of human lung cancer cells in vivo by interacting with alphavbeta3 integrin. Targeting the interaction between OPN and alphavbeta3 integrin could be effective for future development of anti-angiogenic therapeutic agents for patients with lung cancer.     

Insulin-like growth factor 1 is a potent stimulator of cervical cancer cell invasiveness and proliferation that is modulated by alphavbeta3 integrin signaling

Insulin-like growth factor 1 (IGF-1) has been implicated in promoting mitogenic, metastatic and antiapoptotic phenotypes in several types of cancer. But little is known about the signal interaction of IGF-1 and integrin in the regulation of cervical cancer development and progression. This study is to investigate the regulatory mechanism of IGF-1 receptor (IGF-1R) signaling and its importance in cervical cancer formation. The growth and invasiveness of cervical cancer cells (SiHa and CaSki) were dose-dependently stimulated by IGF-1, whereas those of normal cervical epithelial cells were not. The immunoblot showed that IGF-1R proteins were abundant in cervical cancer cell lines. In contrast, IGF-1R protein was nearly undetectable in normal cervical epithelial cells. IGF-1-stimulated invasion and proliferation were abolished by functional-blocking monoclonal antibody against IGF-1R, whereas these cellular functions were unaffected by either IgG or monoclonal antibody to insulin receptor. Functional-blocking monoclonal antibody against integrins alpha(v)beta3, but not alpha2 alpha3, alpha4 alpha6 beta1, beta4 or alpha2beta1, inhibited the IGF-1-stimulated invasion and proliferation in cervical cancer cells. alpha(v)beta3 integrin modulated IGF-1R phosphorylation by altering the rate of Src homology 2-containing phosphotyrosine phosphatase (SHP-2) recruitment to the activated IGF-1R. The modulation of alpha(v)beta3 occupancy also affected the activation of IGF-1R downstream-signaling elements, including activation of Akt and extracellular signal-regulated protein kinases 1/2 (Erk1/2). The treatment of blocking antibody of alpha(v)beta3 integrin or IGF-1R significantly inhibited tumor growth and caused tumor regression in SCID mice model. Immunoblots of tumor tissues confirmed that the phosphorylation of IGF-1R and downstream targets of Akt and Erk1/2 were remarkably decreased in SCID mice treated with blocking antibodies of alpha(v)beta3 or IGF-1R. Thus, these data suggest that the signal interaction between IGF-1R and alpha(v)beta3 integrin plays an important role in promoting the development and progression of cervical cancer.     

A fundamental role for cell cycle regulation in the chemosensitivity of cancer cells?

The majority of clinically effective anticancer drugs inhibit some aspect of the machinery responsible for DNA replication and chromosome segregation. Drug action also arrests cells at defined points in the cell cycle called checkpoints. These checkpoints ensure that subsequent cell cycle events are inhibited until the inflicted damage is repaired. The fidelity of checkpoint control and susceptibility of cells to apoptosis while repair is underway may be important factors in the success of chemotherapy. We discuss these concepts and focus particularly on possible applications to improved antitumor therapy with DNA damaging agents.     

In vivo near-infrared fluorescence imaging of integrin alphavbeta3 in brain tumor xenografts

Noninvasive visualization of cell adhesion molecule alpha(v)beta(3) integrin expression in vivo has been well studied by using the radionuclide imaging modalities in various preclinical tumor models. A literature survey indicated no previous use of cyanine dyes as contrast agents for in vivo optical detection of tumor integrin. Herein, we report the integrin receptor specificity of novel peptide-dye conjugate arginine-glycine-aspartic acid (RGD)-Cy5.5 as a contrast agent in vitro, in vivo, and ex vivo. The RGD-Cy5.5 exhibited intermediate affinity for alpha(v)beta(3) integrin (IC(50) = 58.1 +/- 5.6 nmol/L). The conjugate led to elevated cell-associated fluorescence on integrin-expressing tumor cells and endothelial cells and produced minimal cell fluorescence when coincubated with c(RGDyK). In vivo imaging with a prototype three-dimensional small-animal imaging system visualized subcutaneous U87MG glioblastoma xenograft with a broad range of concentrations of fluorescent probe administered via the tail vein. The intermediate dose (0.5 nmol) produces better tumor contrast than high dose (3 nmol) and low dose (0.1 nmol) during 30 minutes to 24 hours postinjection, because of partial self-inhibition of receptor-specific tumor uptake at high dose and the presence of significant amount of background fluorescence at low dose, respectively. The tumor contrast was also dependent on the mouse viewing angles. Tumor uptake of RGD-Cy5.5 was blocked by unlabeled c(RGDyK). This study suggests that the combination of the specificity of RGD peptide/integrin interaction with near-infrared fluorescence detection may be applied to noninvasive imaging of integrin expression and monitoring anti-integrin treatment efficacy providing near real-time measurements.     

alpha6beta1 integrin expression in hepatocarcinoma cells: regulation and role in cell adhesion and migration.

Liver carcinogenesis is associated with striking changes in the integrin repertoire of hepatocytes, including the overexpression of the laminin and collagen receptors alpha1beta1 and the de novo induction of the laminin receptor alpha6beta1. Our aim was to analyze the role of pro-inflammatory cytokines, interferons and fibrogenic cytokines TGF-beta and FGF2 in the regulation of the expression of beta1 integrins by neoplastic hepatocytes. The 2 human hepatocellular cell lines HepG2 and Hep3B were used as models. Integrin expression was assessed by qualitative methods (immunocytochemistry, Western blotting) and semi-quantitative techniques (FACS, cellular ELISA), before and after stimulation by TNFalpha, IL1-beta, TGF-beta, FGF2, interferon gamma and interferon alpha-2b. HepG2 and Hep3B constitutively expressed alpha1, alpha2, alpha6 and beta1 chains. A 24 to 48-hr stimulation with pro-inflammatory cytokines, TGF-beta and FGF2 induced a significant increase in the concentrations of all integrin chains. The maximum induction was registered for beta1 chain, which presented increases amounting up to 3, 4 and 7 times the control values in the presence of, respectively, TNF alpha/IL1-beta, TGF-beta and FGF2. Interferons had no direct effect on integrin expression and partially antagonized the effects of TNF alpha and TGF-beta. The increased concentrations of integrin chains were associated with an increased membrane expression of the corresponding dimers and with an increased adhesion of stimulated hepatocytes to laminin, which was antagonized by neutralizing anti-beta1 and anti-alpha6 antibodies. Finally, anti-alpha6 antibody inhibited the migration of HepG2 and Hep3B cells in reconstituted basement membrane. Our results suggest that the stimulation of alpha6beta1 integrin expression in hepatocarcinoma cells is essential for cell adhesion and migration.     

Signaling and regulatory mechanisms of integrin alphavbeta6 on the apoptosis of colon cancer cells

Considerable researches have been done about integrin alphanubeta6 and carcinomas, but little information has been shown about the relationship between integrin alphanubeta6 and apoptosis. In this study, we investigated the apoptosis and its related signal pathways to integrin alphavbeta6 in colon cancer cells. After we blocked the function of integrin alphavbeta6 in HT29 cells used the monoclonal antibody, the apoptotic cells increased markedly. Meanwhile, cytochrome C released from mitochondria into cytosol, Bcl-2 decreased while Bax increased significantly, and Fas and Fas-ligand had no change. The activities of caspase-3 and caspase-9 increased, while caspase-8 remained no change. Moreover, the expression of phosphorylated extracellular signal-related kinase (P-ERK) decreased. We confirmed that integrin alphavbeta6 acted as an important role in inhibiting apoptosis in colon cancer cells, and the signaling involved the mitochondrial pathway.     

HS1-associated protein X-1 regulates carcinoma cell migration and invasion via clathrin-mediated endocytosis of integrin alphavbeta6

Enhanced expression levels of integrin alphavbeta6 have been linked to more aggressive invasive carcinoma cell behavior and poorer clinical prognosis. However, how alphavbeta6 determines invasion and the dynamics of integrin alphavbeta6 regulation in tumor cells are poorly understood. We have identified the 35-kDa HS1-associated protein X-1 (HAX-1) protein as a novel binding partner of the beta6 cytoplasmic tail using a yeast two-hybrid screen. We show that alphavbeta6-dependent migration is blocked following small interfering RNA (siRNA)-mediated depletion of HAX-1 in oral squamous cell carcinoma cell lines. Using both siRNA and membrane-permeable peptides, we show that alphavbeta6-dependent migration and invasion require HAX-1 to bind directly to beta6 and thereby regulate clathrin-mediated endocytosis of alphavbeta6 integrins. Progression of oral cancer is associated with enhanced expression of alphavbeta6 and HAX-1 proteins in patient tissue. This report establishes that integrin endocytosis is required for alphavbeta6-dependent carcinoma cell motility and invasion and suggests that this process is an important mechanism in cancer progression.     

A role for cyclic nucleotide phosphodiesterase 4 in regulation of the growth of human malignant melanoma cells

The activity, expression and function of phosphodiesterase 4 (PDE 4) were investigated in the HMG human gingiva-derived malignant melanoma cell line. A specific PDE4 inhibitor, rolipram, inhibited PDE activity in homogenates of HMG cells, and PDE4B and 4D mRNAs were detected by RT-PCR in RNA from HMG cells. Two specific PDE4 inhibitors, rolipram and Ro-20-1724, and an adenylate cyclase activator, forskolin, increased intracellular cAMP in HMG cells. Cell growth induced by rolipram, Ro-20-1724, and forskolin was inhibited by the H-89 protein kinase A (PKA) inhibitor. However, in contrast to effects of H-89, two other PKA inhibitors, KT5720 and PKI, did not inhibit rolipram-induced cell growth. A cAMP analogue that selectively activates Epac, 8-pCPT-2'-O-Me-cAMP, also promoted the growth of HMG cells. These findings suggested that PDE4, PDE4B and/or 4D regulate cell growth through cAMP targets in the HMG malignant melanoma cell line. There have been no previous studies of positive regulation of cell growth by PDE4 inhibition, suggesting that it may be possible to target PDE4 in therapy for human malignant melanoma.