New aspects of integrin signaling in cancer

Integrin signaling in cancer: bidirectional mechanisms and therapeutic opportunities

Integrins are transmembrane receptors that possess distinct ligand-binding specificities in the extracellular domain and signaling properties in the cytoplasmic domain. While most integrins have a short cytoplasmic tail, integrin β4 has a long cytoplasmic tail that can indirectly interact with the actin cytoskeleton. Additionally, 'inside-out' signals can induce integrins to adopt a high-affinity extended conformation for their appropriate ligands. These properties enable integrins to transmit bidirectional cellular signals, making it a critical regulator of various biological processes.Integrin expression and function are tightly linked to various aspects of tumor progression, including initiation, angiogenesis, cell motility, invasion, and metastasis. Certain integrins have been shown to drive tumorigenesis or amplify oncogenic signals by interacting with corresponding receptors, while others have marginal or even suppressive effects. Additionally, different α/β subtypes of integrins can exhibit opposite effects. Integrin-mediated signaling pathways including Ras- and Rho-GTPase, TGFβ, Hippo, Wnt, Notch, and sonic hedgehog (Shh) are involved in various stages of tumorigenesis. Therefore, understanding the complex regulatory mechanisms and molecular specificities of integrins are crucial to delaying cancer progression and suppressing tumorigenesis. Furthermore, the development of integrin-based therapeutics for cancer are of great importance.This review provides an overview of integrin-dependent bidirectional signaling mechanisms in cancer that can either support or oppose tumorigenesis by interacting with various signaling pathways. Finally, we focus on the future opportunities for emergent therapeutics based on integrin agonists. Video Abstract.

Transcriptomic Profile of New Gene Markers Encoding Proteins Responsible for Structure of Porcine Ovarian Granulosa Cells

Simple Summary

The extracellular matrix (ECM) is involved in many physiological processes that occur in the ovary and affect reproduction in animals and humans. The ECM has been shown to significantly affect folliculogenesis, ovulation, and corpus luteum formation. This is mainly due to the involvement of ECM in intercellular signaling. In the present study, we report the gene expression profile of porcine granulosa cells during their primary in vitro culture. The genes presented are related to ECM formation but also to cadherins and integrins that influence intercellular dialogue. During the study, it was shown that most of the genes were upregulated. A detailed understanding of the expression of genes such as POSTN, CHI3L1, CAV-1, IRS1, DCN in in vitro culture of granulosa cells may provide a basis for further studies on the molecular mechanisms occurring within the ovary. Knowledge of ECM-related gene expression within granulosa cells can also be used to study the recently discovered stemness of these cells. Moreover, the presented data may serve for the development of assisted reproduction techniques, which, especially in vitro, are becoming increasingly common.

Abstract

The extracellular matrix (ECM) in granulosa cells is functionally very important, and it is involved in many processes related to ovarian follicle growth and ovulation. The aim of this study was to describe the expression profile of genes within granulosa cells that are associated with extracellular matrix formation, intercellular signaling, and cell–cell fusion. The material for this study was ovaries of sexually mature pigs obtained from a commercial slaughterhouse. Laboratory-derived granulosa cells (GCs) from ovarian follicles were cultured in a primary in vitro culture model. The extracted genetic material (0, 48, 96, and 144 h) were subjected to microarray expression analysis. Among 81 genes, 66 showed increased expression and only 15 showed decreased expression were assigned to 7 gene ontology groups “extracellular matrix binding”, “extracellular matrix structural constituent”, “binding, bridging”, “cadherin binding”, “cell adhesion molecule binding”, “collagen binding” and “cadherin binding involved in cell-cell adhesion”. The 10 genes with the highest expression (POSTN, ITGA2, FN1, LAMB1, ITGB3, CHI3L1, PCOLCE2, CAV1, DCN, COL14A1) and 10 of the most down-regulated (SPP1, IRS1, CNTLN, TMPO, PAICS, ANK2, ADAM23, ABI3BP, DNAJB1, IGF1) were selected for further analysis. The results were validated by RT-qPCR. The current results may serve as preliminary data for further analyses using in vitro granulosa cell cultures in assisted reproduction technologies, studies of pathological processes in the ovary as well as in the use of the stemness potential of GCs.

Pharmacological properties of ginsenosides in inflammation-derived cancers

Ginseng is commonly used as an herbal medicine for improvement of life quality. It is also used as a supplemental medication with anti-cancer drugs to enhance chemotherapy efficacy and shows some beneficial effects. Ginsenosides, also known as saponins, are the major active pharmacological compounds found in ginseng and have been extensively using in treatment of not only cancers but also the other inflammatory diseases such as atherosclerosis, diabetes, acute lung injury, cardiovascular, and infectious diseases. The anti-cancer activities of ginsengs and ginsenosides in different types of cancers have been well studied experimentally and clinically. The major anti-cancer mechanisms of ginseng compounds include inhibition of angiogenesis and metastasis as well as induction of cell cycle arrest and apoptosis. Herein, we review and summarize the current knowledge on the pharmacological effects of ginsengs and ginseng-derived compounds in the treatment of cancers. Moreover, the molecular and cellular mechanism(s) by which ginsengs and ginsenosides modulate the immune response in cancer diseases as well as ginsengs-drugs interaction are also discussed.

Overexpressed ITGA2 contributes to paclitaxel resistance by ovarian cancer cells through the activation of the AKT/FoxO1 pathway

Ovarian cancer is one of the most malignant tumors of the female reproductive system, with high invasiveness. The disease is a severe threat to women's health. The ITGA2 gene, which codes for integrin subunit α2, is involved in the proliferation, invasion, and metastasis of cancer cells. Although previous studies have shown that ITGA2 increases in ovarian cancer, the specific molecular mechanism of how ITGA2 promotes ovarian cancer proliferation and metastasis is still unclear. In this study, we confirmed that ITGA2 was elevated in ovarian cancer, which led to poor prognosis and survival. Overexpressed ITGA2 promoted the proliferation of ovarian cancer cells. We also found that ITGA2 regulated the phosphorylation of forkhead box O1 (FoxO1) by mediating AKT phosphorylation, which provided a reasonable explanation for ITGA2's role in ovarian cancer's resistance to albumin paclitaxel. In summary, ITGA2 could be used as a new therapeutic target and prognostic indicator in ovarian cancer.

Label-free quantitative identification of abnormally ubiquitinated proteins as useful biomarkers for human lung squamous cell carcinomas

BACKGROUND

Ubiquitination is an important molecular event in lung squamous cell carcinoma (LSCC), which currently is mainly studied in nonsmall cell lung carcinoma cell models but lacking of ubiquitination studies on LSCC tissues. Here, we presented the ubiquitinated protein profiles of LSCC tissues to explore ubiquitination-involved molecular network alterations and identify abnormally ubiquitinated proteins as useful biomarkers for predictive, preventive, and personalized medicine (PPPM) in LSCC.

METHODS

Anti-ubiquitin antibody-based enrichment coupled with LC-MS/MS was used to identify differentially ubiquitinated proteins (DUPs) between LSCC and control tissues, followed by integrative omics analyses to identify abnormally ubiquitinated protein biomarkers for LSCC.

RESULTS

Totally, 400 DUPs with 654 ubiquitination sites were identified,, and motifs A-X (1/2/3)-K* were prone to be ubiquitinated in LSCC tissues. Those DUPs were involved in multiple molecular network systems, including the ubiquitin-proteasome system (UPS), cell metabolism, cell adhesion, and signal transduction. Totally, 44 hub molecules were revealed by protein-protein interaction network analysis, followed by survival analysis in TCGA database (494 LSCC patients and 20,530 genes) to obtain 18 prognosis-related mRNAs, of which the highly expressed mRNAs VIM and IGF1R were correlated with poorer prognosis, while the highly expressed mRNA ABCC1 was correlated with better prognosis. VIM-encoded protein vimentin and ABCC1-encoded protein MRP1 were increased in LSCC, which were all associated with poor prognosis. Proteasome-inhibited experiments demonstrated that vimentin and MRP1 were degraded through UPS. Quantitative ubiquitinomics found ubiquitination level was decreased in vimentin and increased in MRP1 in LSCC. These findings showed that the increased vimentin in LSCC might be derived from its decreased ubiquitination level and that the increased MRP1 in LSCC might be derived from its protein synthesis > degradation. GSEA and co-expression gene analyses revealed that VIM and MRP1 were involved in multiple crucial biological processes and pathways. Further, TRIM2 and NEDD4L were predicted as E3 ligases to regulate ubiquitination of vimentin and MRP1, respectively.

CONCLUSION

These findings revealed ubiquitinomic variations and molecular network alterations in LSCC, which is in combination with multiomics analysis to identify ubiquitination-related biomarkers for in-depth insight into the molecular mechanism and therapeutic targets and for prediction, diagnosis, and prognostic assessment of LSCC.

Overexpressed ITGA2 promotes malignant tumor aggression by up-regulating PD-L1 expression through the activation of the STAT3 signaling pathway

Background

Recent studies have reported that Integrin alpha 2 (ITGA2) plays an essential role in tumor cell proliferation, invasion, metastasis, and angiogenesis. An abnormally expressed ITGA2 correlates with unfavorable prognoses in multiple types of cancer. However, the specific mechanism of how ITGA2 contributes to tumorigenesis remains unclear.

Methods

The GEPIA web tool was used to find the clinical relevance of ITGA2 in cancer, and this significance was verified using Western blotting analysis of paired patient tissues and immunohistochemistry of the pancreatic cancer tissue. Functional assays, such as the MTS assay, colony formation assay, and transwell assay, were used to determine the biological role of ITGA2 in human cancer. The relationship between ITGA2 and programmed death-ligand 1 (PD-L1) was examined using Western blot analysis, RT-qPCR assay, and immunohistochemistry. The protein-protein interaction between ITGA2 and STAT3 was detected via co-immunoprecipitation.

Results

Our study showed that ITGA2 was markedly overexpressed in several malignant tumor cells and clinical tissues. Blocking ITGA2 inhibited the proliferation and invasion ability of cancer cells significantly, whereas overexpressed ITGA2 increased the degree of those processes considerably. Additionally, the RNA-seq assay indicated that ITGA2 transcriptionally regulated the expression of PD-L1 in pancreatic cancer. We also demonstrated that ITGA2 interacted with STAT3 and up-regulated the phosphorylation of STAT3; this interaction might involve the mechanism of ITGA2 inducing PD-L1 expression in cancer cells. Our results suggest that ITGA2 plays a critical role in cancer cell progression and the regulation of PD-L1 by activating the STAT3 pathway.

Conclusions

We identified a novel mechanism by which ITGA2 plays a critical role in modulating cancer immune response by transcriptionally increasing the expression of PD-L1 in cancer cells. Thus, targeting ITGA2 is an effective method to enhance the efficacy of checkpoint immunotherapy against cancer.

Heat processing effect of luteolin on anti-metastasis activity of human glioblastoma cells U87

Among the flavonoïds, luteolin is a flavone that has been identified in many plants. It is known for its apoptotic potential with damage to DNA and cell cycle blockage. Many studies have shown that luteolin has anti-oxidant, anti-inflammatory, and anti-cancer activities. However, it is known that heat treatment (boiling, cooking, and treating with microwaves …) can influence the structure of flavonoïds, which often leads to changes in their activities. The present study was conducted to study the effect of heated luteolin on anti-tumor activity of glioblastoma cells U87. Glioblastoma cell viability was evaluated by MTT assay. Adhesion assay was performed on different protein matrices (collagen type 1, vitronectin, fibronectin, and poly-L-lysine); migration assay was determined by modified Boyden chambers and videomicroscopy, and finally, angiogenesis was tested in vitro by capillary network formation on Matrigel™. The results obtained show that the thermal treatment significantly reduces its cytotoxic activity and ability to inhibit cell adhesion to different protein matrices. It was also found that the heat processed significantly reduced the ability of luteolin to inhibit cell migration, cell invasion, and endothelial cell angiogenesis (HMEC-1). This suggests that heat treated luteolin has a lower anti-tumor potential than native luteolin. Graphical abstract ᅟ.

Matrix stiffness regulates arteriovenous differentiation of endothelial progenitor cells during vasculogenesis in nude mice

Objectives

The aim of the study was to investigate the effect of matrix stiffness on arteriovenous differentiation of endothelial progenitor cells (EPCs) during vasculogenesis in nude mice.

Materials and methods

Dextran hydrogels of differing stiffnesses were first prepared by controlling the crosslinking reaction to generate different thioether bonds. Hydrogels with stiffnesses matching those of the arterial extracellular matrix and venous extracellular matrix were separately combined with mouse bone marrow‐derived EPCs and subcutaneously implanted on either side of the backs of nude mice. After 14 days, artery‐specific marker Efnb2 and vein‐specific marker Ephb4 in the neovasculature were detected to determine the effect of matrix stiffness on the arteriovenous differentiation of EPCs in vivo.

Results

Fourteen days after the implantation of the EPC‐loaded dextran hydrogels, new blood vessels were observed in both types of hydrogels. We further verified that matrix stiffness regulated the arteriovenous differentiation of EPCs during vasculogenesis via the Ras/Mek pathway.

Conclusions

Matrix stiffness regulates the arteriovenous differentiation of EPCs during vasculogenesis in nude mice through the Ras/Mek pathway.

Methylation-independent ITGA2 overexpression is associated with poor prognosis in de novo acute myeloid leukemia

Previous studies have been indicated that integrin α2 (ITGA2) may be important in cell migration, invasion, survival, and angiogenesis. However, the correlation between ITGA2 expression and acute myeloid leukemia (AML) is still unclear. Real-time quantitative polymerase chain reaction was carried out to analyze ITGA2 messenger RNA level. Methylation-specific polymerase chain reaction (PCR) and bisulfite sequencing PCR were performed to detect the methylation of ITGA2 promoter. ITGA2 expression was significantly upregulated in 134 de novo AML patients compared with 33 controls (p = 0.007). ITGA2^high group had markedly lower complete remission (CR) rate than ITGA2^low group (p = 0.011). Furthermore, the overall survival in ITGA2^high patients was significantly shorter than ITGA2^low patients throughout AML cohort, non-acute promyelocytic leukemia (APL) and cytogenetic normal-AML (p = 0.001, 0.002, and 0.044, respectively). Multivariate analysis confirmed that ITGA2 overexpression served as an independent prognostic factor in both whole-cohort AML patients (p = 0.018) and non-APL AML patients (p = 0.021). Besides, ITGA2 expression level was significantly decreased in AML patients after CR (p = 0.011), and was returned at the time of relapse phase (p = 0.021). Moreover, unmethylated ITGA2 promoter was identified in normal controls, leukemia cell lines, and primary leukemia cells with low or high ITGA2 expression. In conclusions, methylation-independent ITGA2 overexpression is associated with poor prognosis in AML.

Updating the research on the chemopreventive and therapeutic role of the peptide lunasin

Chronic diseases have become the medical challenge of the 21st century because of their high incidence and mortality rates. Modulation of diet and lifestyle habits is considered as the best strategy for the prevention of these disorders. Health promoting benefits beyond their nutritional effects have been described for multiple dietary compounds. Among these compounds, the peptide lunasin is considered as one of the most promising. Naturally present in soybean, lunasin has been extensively studied in the last two decades because of its potential against chronic diseases such as cancer, cardiovascular and immunological disorders. The purpose of this article is to summarise the evidence on the presence of lunasin in soybean and derived foods, and its bioavailability once it is orally ingested. The protective and therapeutic effects of this peptide against cancer, oxidative stress, inflammation, and high cholesterol levels as well as the molecular mechanisms of action involved in these effects are also described in this review. © 2017 Society of Chemical Industry.

Novel 3-D cell culture system for in vitro evaluation of anticancer drugs under anchorage-independent conditions

Anticancer drug discovery efforts have used 2‐D cell‐based assay models, which fail to forecast in vivo efficacy and result in a lower success rate of clinical approval. Recent 3‐D cell culture models are expected to bridge the gap between 2‐D and in vivo models. However, 3‐D cell culture methods that are available for practical anticancer drug screening have not yet been fully attained. In this study, we screened several polymers for their ability to suspend cells or cell spheroids homogeneously in a liquid medium without changing the viscosity behavior, and identified gellan gum (FP001), as the most potent polymer. FP001 promoted cell dispersion in the medium and improved the proliferation of a wide range of cancer cell lines under low attachment conditions by inhibiting the formation of large‐sized spheroids. In addition, cancer cells cultured with FP001‐containing medium were more susceptible to inhibitors of epidermal growth factor (EGF) signaling than those cultured under attachment conditions. We also showed that ligands of the EGF receptor family clearly enhance proliferation of SKOV3 ovarian carcinoma cells under anchorage‐independent conditions with FP001. Consistent with this result, the cells grown with FP001 showed higher EGF receptor content compared with cells cultured under attachment conditions. In conclusion, we developed a novel 3‐D cell culture system that is available for high throughput screening of anticancer agents, and is suitable for evaluation of molecular‐targeted anticancer drugs. Three‐dimensional cell culture using FP001 will be of value in the development of useful technologies for anticancer drug discovery.

Integrin β1-mediated acquired gefitinib resistance in non-small cell lung cancer cells occurs via the phosphoinositide 3-kinase-dependent pathway

The present study aimed to explore the role of integrin β1 and the relevant signaling pathways in acquired gefitinib resistance in non-small cell lung cancer (NSCLC). The inhibitory effects of gefitinib, with or without LY294002, on cellular proliferation were evaluated by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide assay. Cell cycle progression and apoptosis were analyzed by flow cytometry, while western blotting was used to evaluate the expression of EGFR, phosphorylated (phospho)-EGFR, protein kinase B (Akt), phospho-Akt, extracellular signal-regulated kinase (Erk) and phospho-Erk. The gene expression profiles of PC9 and PC9/G cells were determined by DNA microarray. Integrin β1 was knocked down in PC9/G cells by transiently transfected short interfering RNA (siRNA). A scrambled siRNA sequence was used as a control. Apoptosis of transfected cells was determined by Annexin V-phycoerythrin-Cy5/propidium iodide staining. Sequencing products were amplified by nested PCR. The resistant index of PC9/G cells to gefitinib was ~138- to 256-fold higher than that of PC9 cells, and this resistance was accompanied by significant increase in integrin β1 expression in PC9/G cells. Knockdown of integrin β1 with short hairpin RNA in PC9/G cells markedly inhibited proliferation and enhanced apoptosis in response to gefitinib, restoring the sensitivity of PC9/G cells gefitinib. Phosphoinositide 3-kinase (PI3K)/Akt activation was observed in PC9/G cells in the presence of gefitinib and the sensitivity of PC9/G cells to gefitinib was also able to be restored by PI3K/Akt pathway inhibitor LY294002. Finally, knockdown of integrin β1 significantly reduced the levels of phospho-Akt. These findings suggest that integrin β1 signaling via the PI3K/Akt pathway may be a significant mechanism underlying gefitinib resistance, and may potentially present an alternative therapeutic target for the treatment of NSCLC unresponsive to EGFR inhibitors.

Association of ITGA2 C807T polymorphism with risk of colorectal adenoma and colorectal cancer

AIM: To evaluate the impact of the ITGA2 C807T gene polymorphism on the risk of colorectal adenoma (CRA) and colorectal cancer (CRC) in a Chinese Han population.

METHODS: A hospital-based case-control study was conducted, including 95 healthy controls, 48 patients with CRA and 89 patients with CRC. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Association of the genotypes with the clinical and pathological features of CRC was evaluated.

RESULTS: The frequencies of the genotypes and alleles in CRC were significantly different from those of controls, but there were no significant differences between CRA and controls. Compared with individuals with the wild type genotype CC, subjects with the variant genotypes (CT + TT) had a significantly higher risk of CRA and CRC. In stratified analyses, the elevated CRC risk was especially evident in older individuals, females, smokers, drinkers, well-educated subjects, mental workers and urban subjects. However, no correlation was observed between CRA patients and controls in stratified analyses. When stratified by clinicopathological features such as lesion distribution, pathology subtype, tumor size, differentiation degree, depth of invasion, lymph node metastasis and Duke's stage in patients with CRC, no associations were observed in the polymorphism distributions.

CONCLUSION: The ITGA2 C807T polymorphism may be associated with an increased risk of CRA and CRC.

RhoGTPases - A novel link between cytoskeleton organization and cisplatin resistance

For more than three decades, platinum compounds have been the first line treatment for a wide spectrum of solid tumors. Yet, cisplatin resistance is a major impediment in cancer therapy, and deciphering the mechanisms underlying chemoresistance is crucial for the development of novel therapies with enhanced efficacy. The Rho subfamily of small GTPases plays a significant role in cancer progression, and a growing body of evidence points toward the involvement of these proteins in anticancer drug resistance, including cisplatin resistance. The cycling between active and inactive states, governed by the balance between their GEFs, GAPs and GDIs, RhoGTPases, acts as molecular switches with a pivotal role in actin cytoskeleton organization. The Rho subfamily of proteins is involved in many key cellular processes including adhesion, vesicular trafficking, proliferation, survival, cell morphology and cell-matrix interactions. Although RhoA, RhoB and RhoC are highly homologous and share some upstream regulators and downstream effectors, they each have different roles in cancer progression and chemoresistance. While RhoA and RhoC are upregulated in many tumors and can stimulate transformation, RhoB appears to exhibit tumor suppressor characteristics with proapoptotic effects. In the current review, we discuss the role of Rho subfamily of proteins in cancer, and focus on their involvement in intrinsic and acquired drug resistance.

Synergy of urokinase‑type plasminogen activator receptor isomer (D1D2) and integrin α5β1 causes malignant transformation of hepatic cells and the occurrence of liver cancer

The aim of the present study was to investigate the correlations and possible synergy among the urokinase‑type plasminogen activator receptor (uPAR) isomer D1D2 and integrin α5β1 expression levels, malignant transformation in hepatic cells and the occurrence of liver cancer. The expression site and concentration of uPAR (D1D2) were analyzed using polymerase chain reaction and in situ hybridization at the gene level in 60 samples of hepatocellular carcinoma (HCC) tissues, 60 samples of para‑carcinoma tissues and 25 samples of normal liver tissues. The mRNA levels of uPAR (D1D2) and integrin α5β1 were markedly increased para‑carcinoma tissue and liver cancer tissue as compared with those in normal tissue. The grey values of the three groups were significantly different (P<0.05). In situ hybridization revealed that the expression levels of uPAR (D1D2) and integrin α5β1 in the cytoplasm and the positive rate of the two molecules in the HCC tissue were significantly higher than those in the para-carcinoma and normal liver tissues, and the expression levels were positively correlated (rs1=0.257, P<0.05; rs2=0.261, P<0.05). The results suggested that uPAR (D1D2) mRNA overexpression may be due to changes in the conformation of the uPAR isomer. Synergy of uPAR (D1D2) mRNA and integrin α5β1 interaction may result in abnormal signal transduction in liver cells and ultimately liver cell abnormal clonal hyperplasia and malignant transformation.

AFAP1L1, a novel associating partner with vinculin, modulates cellular morphology and motility, and promotes the progression of colorectal cancers

We have previously identified actin filament-associated protein 1-like 1 (AFAP1L1) as a metastasis-predicting marker for spindle cell sarcomas by gene expression profiling, and demonstrated that AFAP1L1 is involved in the cell invasion process by in vitro analyses. However, its precise molecular function has not been fully elucidated, and it remains unknown whether AFAP1L1 could be a prognostic marker and/or therapeutic target of other malignancies. In this study, we found a marked elevation of AFAP1L1 gene expression in colorectal cancer (CRC) tissues as compared to the adjacent normal mucosa. Multivariate analysis revealed that AFAP1L1 was an independent and significant factor for the recurrence of rectal cancers. Moreover, the addition of the AFAP1L1 expression level to the lymph node metastasis status provided more predictive information regarding postoperative recurrence in rectal cancers. AFAP1L1-transduced CRC cells exhibited a rounded shape, increased cell motility on planar substrates, and resistance to anoikis in vitro. AFAP1L1 localized to the ringed structure of the invadopodia, together with vinculin, and AFAP1L1 was identified as a novel associating partner of vinculin by immunoprecipitation assay. AFAP1L1-transduced cells showed accelerated tumor growth in vivo, presumably reflecting the anoikis resistance of these AFAP1L1-expressing cells. Furthermore, the local administration of a siRNA against AFAP1L1 significantly suppressed the in vivo tumor growth of xenografts, suggesting that AFAP1L1 might be a candidate therapeutic target for CRCs. These results suggest that AFAP1L1 plays a role in the progression of CRCs by modulating cell shape and motility and by inhibiting anoikis, presumably through interactions with vinculin-including protein complexes.

High-level β1-integrin expression in a subpopulation of highly tumorigenic oral cancer cells

OBJECTIVES

The β1 integrin (CD29) is a putative marker for cancerous epithelial stem cells. Cancer stem cells are essential to drive tumor growth, recurrence, and metastasis. We investigated the role of β1-integrin expression in the development of malignant phenotypes of oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Immunostaining was used to analyze the expression levels of β1 integrins in different types of cell colonies and tumor spheres. The results of cell viability and migration assays with and without siRNA knockdown of β1-integrin expression were compared. Cells expressing β1 integrins were evaluated for their tumorigenicity in mice. The expression of β1 integrins in human specimens of oral cancers at different clinical stages was semiquantified based on immunohistochemical staining of the β1-integrin protein.

RESULTS

The expression level of β1 integrins in Meng-1 oral epidermoid carcinoma cells (OECM-1) cells was significantly higher in holoclonal colonies and tumor spheres compared to control cells. The knockdown of β1-integrin expression in OECM-1 cells reduced cell proliferation, migration, and tumor sphere formation. Beta-1 integrin (+) cells were more tumorigenic in the mouse xenograft model than β1 integrin (-) cells. In the human specimens, the expression level of the β1-integrin protein positively correlated with the clinical stage.

CONCLUSION

The expression of β1 integrin in OECM-1 cells is involved in the development of malignant phenotypes of OSCC.

CLINICAL RELEVANCE

Inhibitors for β1-integrin signaling may be suitable to become target-specific therapies for OSCC.

Association study of integrins beta 1 and beta 2 gene polymorphism and papillary thyroid cancer

BACKGROUND

We investigated whether single nucleotide polymorphisms (SNPs) of integrin beta 1 (ITGB1) and integrin beta 2 (ITGB2) contribute to the development of papillary thyroid cancer (PTC).

METHODS

Two synonymous SNPs (rs2230396 and rs2298141) of ITGB1 and 1 synonymous SNP (rs2352326), 1 5' URT-region SNP (rs2070947), and 1 promoter SNP (rs2070946) of ITGB2 SNPs were genotyped using direct sequencing in 94 patients with PTC and 213 healthy controls. Genetic data were analyzed using SNPStats (http://bioinfo.iconcologia.net/SNPstats), Helix Tree (Golden Helix Inc, Bozeman, MT), and SNPAnalyzer (ISTECH Corp, Goyang City, Republic of Korea).

RESULTS

The promoter SNP (rs2070946) of ITGB2 was significantly associated with the development of PTC (dominant model, log-additive model). The G allele frequencies of the promoter SNP (rs2070946) of ITBG2 in patients with PTC (19.9%) were increased by about 2-fold compared with controls (10.2%).

CONCLUSIONS

Our results suggest that a promoter SNP (rs2070946) of ITGB2 might be associated with a risk of PTC.

PIVL, a new serine protease inhibitor from Macrovipera lebetina transmediterranea venom, impairs motility of human glioblastoma cells

A novel Kunitz-type serine proteinase inhibitor, termed PIVL, was purified to homogeneity from the venom of the Tunisian snake Macrovipera lebetina transmediterranea. It is a monomeric polypeptide chain cross-linked by three disulfide linkages with an isotope-averaged molecular mass of 7691.7 Da. The 67-residue full-length PIVL sequence was deduced from a venom gland cDNA clone. Structurally, PIVL is built by a single Kunitz/BPTI-like domain. Functionally, it is able to specifically inhibit trypsin activity. Interestingly, PIVL exhibits an anti-tumor effect and displays integrin inhibitory activity without being cytotoxic. Here we show that PIVL is able to dose-dependently inhibit the adhesion, migration and invasion of human glioblastoma U87 cells. Our results also show that PIVL impairs the function of αvβ3 and to a lesser extent, the activity of αvβ6, αvβ5, α1β1 and α5β1 integrins. Interestingly, we demonstrate that the (41)RGN(43) motif of PIVL is likely responsible for its anti-cancer effect. By using time lapse videomicroscopy, we found that PIVL significantly reduced U87 cells motility and affected cell directionality persistence by 68%. These findings reveal novel pharmacological effects for a Kunitz-type serine proteinase inhibitor.

Elevated expression of integrin αv and β5 subunit in laryngeal squamous-cell carcinoma associated with lymphatic metastasis and angiogenesis

In the past several years, the αv integrin subfamily has been repeatedly found to be involved in tumor progression and angiogenesis. The aim of this study was to investigate the expression of the integrin αv subfamily in laryngeal squamous cell carcinoma (LSCC), and to correlate the expression rate with tumor biological behavior and angiogenesis of the LSCC. The integrin αv subfamily, including αv, β1, β3, β5, β6 and β8 subunits, was immunohistochemically found to be expressed in 64 patients with LSCC, and we analyzed the relationship between the expression rate and the clinicopathological stage of this cancer. Immunohistochemical staining for CD105 was carried out in the same group of the patients. The intratumoral microvessel density (IMVD) of the LSCC was calculated by CD105 staining, and the correlation between the IMVD and αv subfamily expression was discussed. The results showed that all members of the integrin αv subfamily could be detected in the LSCC. The expression rate of integrin αv and β5 subunits in primary cancer was significantly higher than in normal tissue, and their expression rate in the group with lymphatic metastasis was significantly higher than in the group without metastasis. The IMVD of the group with positive expression of αv and β5 subunits was significantly higher than in the group with negative expression, but there were no significant effects on the β1, β3, β6 and β8 subunits in these biological processes. In conclusion, the expressions of integrin αv and β5 subunits were significantly associated with lymphatic metastasis and angiogenesis of the LSCC. Among the members of integrin αv subfamily, integrin αvβ5 might play an important role in invasion and metastases of the LSCC, and it may become a valuable marker for the evolution of the LSCC.

Prospero homeobox 1 promotes epithelial-mesenchymal transition in colon cancer cells by inhibiting E-cadherin via miR-9

PURPOSE

Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer.

EXPERIMENTAL DESIGN

Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelial-mesenchymal transition (EMT).

RESULTS

PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P = 0.00005), advanced tumor staging (P = 0.005), and lymph node metastasis (P = 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of E-cadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3'UTR reporter activity and protein expression. Anti-miR-9 restored E-cadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin.

CONCLUSIONS

Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer.

Rab25 is a tumor suppressor gene with antiangiogenic and anti-invasive activities in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC), the major histologic subtype of esophageal cancer, is a devastating disease characterized by distinctly high incidences and mortality rates. However, there remains limited understanding of molecular events leading to development and progression of the disease, which are of paramount importance to defining biomarkers for diagnosis, prognosis, and personalized treatment. By high-throughout transcriptome sequence profiling of nontumor and ESCC clinical samples, we identified a subset of significantly differentially expressed genes involved in integrin signaling. The Rab25 gene implicated in endocytic recycling of integrins was the only gene in this group significantly downregulated, and its downregulation was confirmed as a frequent event in a second larger cohort of ESCC tumor specimens by quantitative real-time PCR and immunohistochemical analyses. Reduced expression of Rab25 correlated with decreased overall survival and was also documented in ESCC cell lines compared with pooled normal tissues. Demethylation treatment and bisulfite genomic sequencing analyses revealed that downregulation of Rab25 expression in both ESCC cell lines and clinical samples was associated with promoter hypermethylation. Functional studies using lentiviral-based overexpression and suppression systems lent direct support of Rab25 to function as an important tumor suppressor with both anti-invasive and -angiogenic abilities, through a deregulated FAK-Raf-MEK1/2-ERK signaling pathway. Further characterization of Rab25 may provide a prognostic biomarker for ESCC outcome prediction and a novel therapeutic target in ESCC treatment.

Dynamics of cell attachment: adhesion time and force

Due to its biological significance, cell adhesion to biomaterial surfaces or scaffolds is the key step in biomedical applications. Here, we describe two sensitive and facile methods that quantify the kinetic and mechanic properties of the entire cell attachment process characterized by two parameters: Adhesion Time T(Ad) and Adhesion Force F(Ad). We demonstrate that both methods can be applied to any adherent cell type (e.g., stem or cancer cells), tissue-engineered substrate, and culture condition in a fast, effective, and reproducible manner. Additional investigations about the role of the extracellular matrix and the formation of focal contacts help in acquiring further interpretations of these parameters from biological and mechanical points of view.

The effects of a plant proteinase inhibitor from Enterolobium contortisiliquum on human tumor cell lines

Supplementary to the efficient inhibition of trypsin, chymotrypsin, plasma kallikrein, and plasmin already described by the EcTI inhibitor from Enterolobium contortisiliquum, it also blocks human neutrophil elastase (K(iapp)=4.3 nM) and prevents phorbol ester (PMA)-stimulated activation of matrix metalloproteinase (MMP)-2 probably via interference with membrane-type 1 (MT1)-MMP. Moreover, plasminogen-induced activation of proMMP-9 and processing of active MMP-2 was also inhibited. Furthermore, the effect of EcTI on the human cancer cell lines HCT116 and HT29 (colorectal), SkBr-3 and MCF-7 (breast), K562 and THP-1 (leukemia), as well as on human primary fibroblasts and human mesenchymal stem cells (hMSCs) was studied. EcTI inhibited in a concentration range of 1.0-2.5 μM rather specifically tumor cell viability without targeting primary fibroblasts and hMSCs. Taken together, our data indicate that the polyspecific proteinase inhibitor EcTI prevents proMMP activation and is cytotoxic against tumor cells without affecting normal tissue remodeling fibroblasts or regenerative hMSCs being an important tool in the studies of tumor cell development and dissemination.

Targeting of α(v)-integrins in stem/progenitor cells and supportive microenvironment impairs bone metastasis in human prostate cancer

Acquisition of an invasive phenotype by cancer cells is a requirement for bone metastasis. Transformed epithelial cells can switch to a motile, mesenchymal phenotype by epithelial-mesenchymal transition (EMT). Recently, it has been shown that EMT is functionally linked to prostate cancer stem cells, which are not only critically involved in prostate cancer maintenance but also in bone metastasis. We showed that treatment with the non-peptide α(v)-integrin antagonist GLPG0187 dose-dependently increased the E-cadherin/vimentin ratio, rendering the cells a more epithelial, sessile phenotype. In addition, GLPG0187 dose-dependently diminished the size of the aldehyde dehydrogenase high subpopulation of prostate cancer cells, suggesting that α(v)-integrin plays an important role in maintaining the prostate cancer stem/progenitor pool. Our data show that GLPG0187 is a potent inhibitor of osteoclastic bone resorption and angiogenesis in vitro and in vivo. Real-time bioluminescent imaging in preclinical models of prostate cancer demonstrated that blocking α(v)-integrins by GLPG0187 markedly reduced their metastatic tumor growth according to preventive and curative protocols. Bone tumor burden was significantly lower in the preventive protocol. In addition, the number of bone metastases/mouse was significantly inhibited. In the curative protocol, the progression of bone metastases and the formation of new bone metastases during the treatment period was significantly inhibited. In conclusion, we demonstrate that targeting of integrins by GLPG0187 can inhibit the de novo formation and progression of bone metastases in prostate cancer by antitumor (including inhibition of EMT and the size of the prostate cancer stem cell population), antiresorptive, and antiangiogenic mechanisms.

Phosphoinositides in cell architecture

Inositol phospholipids have been implicated in almost all aspects of cellular physiology including spatiotemporal regulation of cellular signaling, acquisition of cellular polarity, specification of membrane identity, cytoskeletal dynamics, and regulation of cellular adhesion, motility, and cytokinesis. In this review, we examine the critical role phosphoinositides play in these processes to execute the establishment and maintenance of cellular architecture. Epithelial tissues perform essential barrier and transport functions in almost all major organs. Key to their development and function is the establishment of epithelial cell polarity. We place a special emphasis on highlighting recent studies demonstrating phosphoinositide regulation of epithelial cell polarity and how individual cells use phosphoinositides to further organize into epithelial tissues.

Association between ITGA2 C807T polymorphism and gastric cancer risk

AIM: To evaluate the impact of the ITGA2 gene polymorphism on gastric cancer risk.

METHODS: A hospital-based case-control study was conducted, including 307 gastric cancer patients and 307 age- and gender-matched control subjects. The genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS: The frequencies of the wild and variant genotypes in cases were significantly different from those of controls (P = 0.019). Compared with individuals with the wild genotype CC, subjects with the variant genotypes (CT + TT) had a significantly higher risk of gastric cancer (adjusted odds ratio = 1.57, 95% CI = 1.13-2.17, P = 0.007). In stratified analyses, the elevated gastric cancer risk was especially evident in older individuals aged > 58 years, nonsmokers and rural subjects. Further analyses revealed that the variant genotypes were associated with poor tumor differentiation and adjacent organ invasion in the sub-analysis of gastric cancer patients.

CONCLUSION: The ITGA2 gene C807T polymorphism may be associated with an increased risk of gastric cancer, differentiation and invasion of gastric cancer.

Talin-1 overexpression defines high risk for aggressive oral squamous cell carcinoma and promotes cancer metastasis

Oral squamous cell carcinoma (OSCC) is highly invasive and is associated with frequent tumour recurrences and lymph node metastases. Identification of genes involved in the aggressiveness of OSCC may provide new targets for clinical intervention. A genome-wide study based on the Sty1 250K SNP array indicated the involvement of the Talin-1 (TLN1) gene in the 9p13.3 amplicon, which was further validated by dual colour fluorescence in situ hybridization (FISH). Comparative analyses revealed that TLN1 was the most highly expressed integrin-cytoskeleton cross-linker that can trigger integrin activation. IHC analyses and mouse study also revealed an association between TLN1 overexpression and advanced OSCC with invasion to adjacent tissues. Survival analyses indicated a significant association between TLN1 genetic gain/overexpression and a reduced overall survival in patients. Functional knockdown by a dominant negative TLN1 fragment reduced cell growth and invasiveness in TLN1-overexpressing cells via inactivation of downstream oncogenic signalling. The present study suggests an important role for TLN1 in oral cancer development. TLN1 overexpression could serve as a diagnostic marker for aggressive phenotypes and a potential target for treating OSCC.

The sensors and regulators of cell-matrix surveillance in anoikis resistance of tumors

Normal cells continuously monitor the nature of their respective cellular microenvironment. They are equipped with an inherent molecular defense to detect changes that can precipitate and trigger an oncogenic cascade in the internal and external environment of cells. The process called anoikis unleashes many a characteristic molecular change in the cells which eventually program to cell death in response to cell detachment and inappropriate cellular attachment, both of which can otherwise potentiate the ability of cells to preferentially pursue a malignant course due to the release of molecular discipline which conforms them to a benign structural and functional spectrum. The initiation and propagation of signaling that serves as a switch to cell survival or cell death mediated by surveillance of cell microenvironment is comprised of many heterogeneous sets of molecules interacting mainly at the interface of cell-extracellular matrix. Transforming cells continuously reprogram their signaling characteristics in sensing and modulating the stimuli from cell surface molecules like integrins, cadherins and immunoglobulin family of cell adhesion molecules at adhesion complexes, which enables them to resist anoikis and metastasize to different organs. Actin cytoskeleton binds BIM and Bcl2 modifying factor (BMF), which are regulated by the adhesion status and consequent conformation of cytoskeleton in the cells. This review aims at an integrated synopsis of fundamental mechanisms of the critical interactions of cell surface molecules to facilitate a focused analysis of the differential regulation of signaling processes at cell-ECM junctions that collectively rein the anoikis resistance, which in turn impacts metastatic aggressiveness and drug resistance of tumors originating from respective organs.

The disintegrin contortrostatin in combination with docetaxel is a potent inhibitor of prostate cancer in vitro and in vivo

BACKGROUND

There are few available treatments for hormone refractory prostate cancer. Through the inhibition of integrins, contortrostatin (CN) effects tumor cell growth directly as well as through the inhibition of angiogenesis. The effect of CN in combination with docetaxel on prostate cancer cell lines in vitro and in vivo is evaluated in the present study.

METHODS

FACS analysis of integrin expression, assessment of CN and docetaxel exposure on viability of plated cancer cells, and scratch test migration analysis were performed on PC-3 prostate cancer cells. CN and docetaxel inhibition of both PC-3 and CWR-22 prostate cancer cell lines were evaluated in a mouse xenograft bone model. Angiogenic activity in tumors were assessed using IHC with antibodies to CD31.

RESULTS

Cell culture experiments indicate that the combination of docetaxel and CN inhibits growth in an additive fashion. FACS analysis of PC-3 cells shows expression of alpha5beta1 and alphavbeta5 integrins, but little expression of the alphavbeta3. CN showed complete inhibition of PC-3 migration in cultures grown on matrigel plates. In mice xenograft bone models, CN with docetaxel showed increased inhibition of both PC-3 and CWR-22 derived tumors. Analysis of treated xenograft tumors showed significantly decreased expression of CD31 indicating suppression of angiogenesis.

Effects of down-regulation of integrin-beta1 expression on migration and hepatic metastasis of human colon carcinoma

Organ-specific tumor cell adhesion to extracellular matrix (ECM) components and cell migration into host organs often involve integrin-mediated cellular processes. Direct integrin-mediated cell adhesion to ECM components in the space of Disse appears to be required for the successful liver metastatic formation of colon cancer. In the present study, human colon cancer HT-29 cells were transfected by liposome with integrin-beta1 antisense oligodeoxynucleotide (ASODN). The integrin-beta1 gene expression in HT-29 cells was significantly down-regulated. The migration of HT-29 cells was assayed using transwell cell culture chambers in vitro. The number of migrating HT-29 cells in experimental group was far less than that in control group (P<0.05). The models of hepatic metastasis in nude mice were established by the intrasplenic injection of transfected HT-29 cells. Thirty days later, the nude mice were killed and the average number of hepatic metastases (4.00+/-0.93 per mouse), average volume (10.10+/-6.50 mm3 per mouse), average weight (0.0440+/-0.0008 g per mouse) in experimental group were remarkably reduced as compared with those in control group (P<0.05). Integrin-beta1 expression in the hepatic metastasis was studied by immunohistochemistry (SP). Positive cell percentage of hepatic metastases in experimental group was markedly decreased as compared with that in control group (P<0.05). It was concluded that integrin-beta1 may take part in hepatic metastasis, and down-regulation of integrin-beta1 expression may play a key role in decreasing migration and hepatic metastasis of human colon carcinoma cells (HT-29).

Lumican inhibits cell migration through α2β1 integrin

Lumican, an extracellular matrix protein of the small leucine-rich proteoglycan family, has been shown to impede melanoma progression by inhibiting cell migration. In the present study, we show that lumican targets α2β1 integrin thereby inhibiting cell migration. A375 melanoma cells were transfected with siRNA directed against the α2 integrin subunit. Compared to A375 control cells, the anti-migratory effect of lumican was abrogated on transfected A375 cells. Moreover, lumican inhibited the chemotactic migration of Chinese hamster ovary (CHO) cells stably transfected with α2 integrin subunit (CHO-A2) but not that of wild-type CHO cells (CHO-WT) lacking this subunit. In contrast to CHO-WT cells, we observed in time-lapse microscopy a decrease of CHO-A2 cell migration speed in presence of lumican. Focal adhesion kinase phosphorylated at tyrosine-397 (pFAK) and total FAK were analysed in CHO-WT and CHO-A2 cells. A significant decrease of the ratio pFAK/FAK was shown in presence of recombinant human lumican. Using solid phase assays, a direct binding between lumican and the α2β1 integrin was demonstrated. This interaction did not involve the glycan moiety of lumican and was cation independent. Lumican was also able to bind the activated I domain of the α2 integrin subunit with a K(d)≥200nM. In conclusion, we demonstrated for the first time that the inhibition of cell migration by lumican depends on a direct binding between the core protein of lumican and the α2β1 integrin.

A novel RGD-toxin protein, Lj-RGD3, from the buccal gland secretion of Lampetra japonica impacts diverse biological activities

RGD (Arg-Gly-Asp) motif toxin proteins from snake venoms, saliva glands secretion of leech or tick have typical characteristics of inhibiting platelet aggregation, angiogenesis, and tumor growth. Here we report cloning and characterization of a novel RGD-toxin protein from the buccal gland of Lampetra japonica. In an attempt to study the activities of anticoagulant in the buccal gland secretion of L. japonica, we established buccal gland cDNA library and identified a gene encoding a predicted protein of 118 amino acids with 3 RGD motifs. The predicted protein was named Lj-RGD3. We generated the cDNA of Lj-RGD3 and obtained the recombinant protein rLj-RGD3. The polyclonal antibodies against rLj-RGD3 recognized the native Lj-RGD3 protein in buccal gland secretion in Western blot analyses. The biological function studies reveal that rLj-RGD3 inhibited human platelet aggregation in a dose-dependent manner with IC(50) value at 5.277 μM. In addition, rLj-RGD3 repressed bFGF-induced angiogenesis in the chick chorioallantoic membrane model. rLj-RGD3 also inhibited the adhesion of ECV304 cells to vitronectin. Furthermore, rLj-RGD3 induced apoptosis and significantly inhibited proliferation, migration, and invasion evoked by bFGF in ECV304 cells. Taken together, these results suggested that rLj-RGD3 is a novel RGD-toxin protein possessing typical functions of the RGD-toxin protein.

Blood monocytes stimulate migration of human pancreatic carcinoma cells in vitro: the role of tumour necrosis factor - alpha

In some types of cancers, tumour-infiltrating monocytes/macrophages (TIM) may be responsible for the formation of an invasive microenvironment in a manner dependent on the secretion of soluble mediators such as tumour necrosis factor-alpha (TNF). Human pancreatic carcinoma (HPC-4) cells are able to induce TNF production by monocytes. Here, the effect of human peripheral blood monocytes, precursors of TIM, on the motility of co-cultured HPC-4 cells, was directly analysed in vitro. A phenotypic transition, i.e., the appearance of rear-front polarised HPC-4 cells paralleled by their increased motility, and increased motility of monocytes, were observed. This effect was attenuated when HPC-4 cells and monocytes were co-cultured in the presence of inhibitors of TNF production and anti-TNF monoclonal antibodies, indicating the specific role of this cytokine in determining paracrine loops between monocytes and cancer cells. Moreover, exogenous TNF induced HPC-4 cell motility concomitantly to the appearance of cellular features characteristic for epithelial-mesenchymal transition (EMT) such as rear-front polarisation, rearrangements of the actin cytoskeleton characteristic for motile cells and the induction of Snail-1 expression. Since cell movement is crucial for cancer invasion and the formation of metastases, these findings demonstrate an EMT-dependent mechanism of cancer progression which acts through the phenotypic transition of pancreatic cancer cells dependent on monocyte-derived TNF.

beta1 integrin is necessary for ureteric bud branching morphogenesis and maintenance of collecting duct structural integrity

The kidney collecting system develops from branching morphogenesis of the ureteric bud (UB). This process requires signaling by growth factors such as glial cell line derived neurotrophic factor (GDNF) and fibroblast growth factors (FGFs) as well as cell extracellular matrix interactions mediated by integrins. The importance of integrin signaling in UB development was investigated by deleting integrin beta1 at initiation (E10.5) and late (E18.5) stages of development. Deletion at E10.5 resulted in a severe branching morphogenesis phenotype. Deletion at E18.5 did not alter renal development but predisposed the collecting system to severe injury following ureteric obstruction. beta1 integrin was required for renal tubular epithelial cells to mediate GDNF- and FGF-dependent signaling despite normal receptor localization and activation in vitro. Aberrations in the same signaling molecules were present in the beta1-null UBs in vivo. Thus beta1 integrins can regulate organ branching morphogenesis during development by mediating growth-factor-dependent signaling in addition to their well-defined role as adhesion receptors.

Integrin alpha-2 and beta-3 gene polymorphisms and colorectal cancer risk

BACKGROUND AND AIMS

Integrins such as alpha(2)beta(1), alpha(IIb)beta(3), and alpha(v)beta(3) have been suggested as key players for cancer development and progression. Several polymorphisms affecting these molecules, two in integrin alpha(2) (ITGA2 807C>T and 1648G>A) and one in beta(3) (ITGB3 176T>C), influence their levels, structure, and possibly their function. To analyze the role of ITGA2 and ITGB3 polymorphisms for colorectal cancer risk and clinical presentation, we performed a case-control study.

MATERIALS AND METHODS

Four hundred thirty-three colorectal cancer patients and 433 healthy sex- and age-matched control subjects were investigated. ITGA2 and ITGB3 polymorphisms were determined by 5'-nuclease assays.

RESULTS/FINDINGS

The ITGA2 807C>T polymorphism was associated with reduced colorectal cancer risk. In a codominant model, the odds ratio for each additional 807-T allele for colorectal cancer was 0.77 (95% confidence interval 0.64-0.94; p = 0.011). The ITGA2 1648G> and the ITGB3 176T>C polymorphism were not associated with colorectal cancer. None of the three polymorphisms investigated was associated with tumor size, histological grade, presence of primary lymph node metastases, tumor stage, or age at diagnosis.

INTERPRETATION/CONCLUSION

We conclude that the ITGA2 807C>T polymorphism may be associated with reduced colorectal cancer risk.

Integrin beta3 down-regulates invasive features of ovarian cancer cells in SKOV3 cell subclones

PURPOSE

To investigate the role of integrin beta3 in invasive features of ovarian cancer SKOV3 cells, by comparing different metastatic subclones.

METHODS

In the present study, two cell subclones, termed as S1 and S21, which possessed high and low metastatic potential, respectively, were isolated and established from human ovarian cancer parental cell line SKOV3 by the limited dilution method. The expressions of integrin alphav, integrin alphavbeta3, integrin beta3, E-cadherin, FAK and ILK in the two cell subclones were compared by means of real-time RT-PCR or flow cytometry. Subsequently, S21 was transfected with siRNA for integrin beta3 and the effects of transfection were examined by methyl thiazolyl tetrazolium (MTT) assay, colony formation assay, Matrigel invasion assay and cell migration assay.

RESULTS

The expressions of integrin alphavbeta3, integrin beta3 and E-cadherin were markedly down-regulated in S1; however, there were no significant differences in the expressions of integrin alphav, FAK and ILK beta. Of note, more than 70% knockdown of integrin beta3 expression was obtained by siRNA technique. The integrin beta3-siRNA-transfected cells showed significant increases in cell proliferation, cell migration and invasive activity in contrast with the mock-transfected cells. The expressions of integrin alphavbeta3 and E-cadherin were lower in the integrin beta3-siRNA-transfected cells compared to the mock control.

CONCLUSION

Integrin beta3, like E-cadherin, may be also a suppressor gene down-regulating invasive features of ovarian cancer cells in SKOV3 cell subclones.

Integrins in prostate cancer progression

Integrins, which are transmembrane receptors for extracellular matrix proteins, play a key role in cell survival, proliferation, migration, gene expression, and activation of growth factor receptors. Their functions and expression are deregulated in several types of cancer, including prostate cancer. In this article, we review the role of integrins in prostate cancer progression and their potential as therapeutic targets.

Selective amino acid restriction differentially affects the motility and directionality of DU145 and PC3 prostate cancer cells

We previously found that selective restriction of amino acids inhibits invasion of two androgen-independent human prostate cancer cell lines, DU145 and PC3. Here we show that the restriction of tyrosine (Tyr) and phenylalanine (Phe), methionine (Met) or glutamine (Gln) modulates the activity of G proteins and affects the balance between two actin-binding proteins, cofilin and profilin, in these two cell lines. Selective amino acid restriction differentially reduces G protein binding to GTP in DU145 cells. Tyr/Phe deprivation reduces the amount of Rho-GTP and Rac1-GTP. Met deprivation reduces the amount of Ras-GTP and Rho-GTP, and Gln deprivation decreases Ras-GTP, Rac-GTP, and Cdc42-GTP. Restriction of these amino acids increases the amount of profilin, cofilin and phosphorylation of cofilin-Ser(3). Increased PAK1 expression and phosphorylation of PAK1-Thr(423), and Ser(199/204) are consistent with the increased phosphorylation of LIMK1-Thr(508). In PC3 cells, Tyr/Phe or Gln deprivation reduces the amount of Ras-GTP, and all of the examined amino acid restrictions reduce the amount of profilin. PAK1, LIMK1 and cofilin are not significantly altered. These data reveal that specific amino acid deprivation differentially affects actin dynamics in DU145 and PC3. Modulation on Rho, Rac, PAK1, and LIMK1 likely alter the balance between cofilin and profilin in DU145 cells. In contrast, profilin is inhibited in PC3 cells. These effects modulate directionality and motility to inhibit invasion.

Integrin-dependent translational control: Implication in cancer progression

The importance of translational control in cancer progression has been underscored by a number of recent studies. However, little is known how cancer cells maintain their high efficiency of translation. Here, we summarize studies that support the role of integrins in translational control, especially at the initiation step, and discuss the various mechanisms by which integrins regulate the recruitment of translational machinery. This review also examines the hypothesis that integrins contribute to various aspects of cancer progression such as proliferation, survival, angiogenesis, and invasion through translational control.

The Role of Integrins in Cancer and the Development of Anti-Integrin Therapeutic Agents for Cancer Therapy

Integrins have been reported to mediate cell survival, proliferation, differentiation, and migration programs. For this reason, the past few years have seen an increased interest in the implications of integrin receptors in cancer biology and tumor cell aggression. This review considers the potential role of integrins in cancer and also addresses why integrins are present attractive targets for drug design. It discusses of the several properties of the integrin-based chemotherapeutic agents currently under consideration clinically and provides an insight into cancer drug development using integrin as a target.

Integrin dependence of Calu-1 cell motility on endothelial extracellular matrix proteins

We recently showed that the motility of the malignant Calu-1 human epidermoid lung carcinoma cells correlates to their expression levels of alpha2, alpha3, alpha6, and beta1 integrin subunits. To determine a causative relationship underlying this correlation, here we measured Calu-1 cell adhesion to and migration on laminin, collagen IV, human umbilical vein endothelial cell monolayers, and endothelial cell extracellular matrix in the presence of function-blocking antibodies against the suspect integrin subunits. Blocking individual alpha subunits did not affect adhesion to or motility on laminin, but when used in pair-wise combinations, monoclonal antibody treatments significantly decreased tumor cell motility on, without diminishing adhesion to, laminin and the other substrates. Blocking all three alpha subunits at once or the beta1 subunit alone abolished migration on laminin; however, the latter treatment also abolished adhesion, whereas the former treatment did not. By contrast, blocking the beta1 subunit significantly reduced motility on collagen IV, endothelial cell monolayers, and endothelial cell extracellular matrix, but always without affecting adhesion. These results suggest a separation of roles and mechanisms of different integrins in adhesion and motility.