VEGFR2 expression and relationship between tumor neovascularization and histologic characteristics in oral squamous cell carcinoma

Establishment of an oral squamous cell carcinoma cell line expressing vascular endothelial growth factor a and its two receptors

Background/purpose

Vascular endothelial growth factor receptor (VEGFR) expression in oral squamous cell carcinoma (OSCC) promotes tumor growth through both autocrine and paracrine signaling. VEGF-positive OSCC cases are associated with a high depth of invasion, increased metastasis, and poor prognosis. In this study we established and then molecularly and functionally analyzed an OSCC cell line that co-expresses VEGF-A, VEGFR-1, and VEGFR-2, termed HCM-SqCC010 cells.

Materials and methods

VEGF-A, VEGFR-1, and VEGFR-2 expression in HCM-SqCC010 cells were examined by immunohistochemistry and immunoblotting. Expression and inhibition of VEGF-A, VEGFR-1, and VEGFR-2 in HCM-SqCC010 cells were verified by quantitative real-time PCR.

Results

Our analysis of HCM-SqCC010 cells revealed that their proliferation depended on VEGF-A, and selective inhibition of VEGFR-1 or VEGFR-2 resulted in decreased cell growth.

Conclusion

We established an OSCC cell line, HCM-SqCC010, that expresses VEGF-A, VEGFR-1, and VEGFR-2. This triple-positive cell line showed no effect from a molecular targeted drug toward VEGF-A, but it did show strong cell growth inhibition in response to a VEGFR inhibitor. Thus, new therapeutic strategies against OSCC should include a VEGFR inhibitor.

Isomangiferin, a Novel Potent Vascular Endothelial Growth Factor Receptor 2 Kinase Inhibitor, Suppresses Breast Cancer Growth, Metastasis and Angiogenesis

Purpose

Vascular endothelial growth factor (VEGF) signal transduction mainly depends on its binding to VEGF receptor 2 (VEGFR-2). VEGF downstream signaling proteins mediate several of its effects in cancer progression, including those on tumor growth, metastasis, and blood vessel formation. The activation of VEGFR-2 signaling is a hallmark of and is considered a therapeutic target for breast cancer. Here, we report a study of the regulation of the VEGFR-2 signaling pathway by a small molecule, isomangiferin.

Methods

A human breast cancer xenograft mouse model was used to investigate the efficacy of isomangiferin in vivo. The inhibitory effect of isomangiferin on breast cancer cells and the underlying mechanism were examined in vitro.

Results

Isomangiferin suppressed tumor growth in xenografts. In vitro, isomangiferin treatment inhibited cancer cell proliferation, migration, invasion, and adhesion. The effect of isomangiferin on breast cancer growth was well coordinated with its suppression of angiogenesis. A rat aortic ring assay revealed that isomangiferin significantly inhibited blood vessel formation during VEGF-induced microvessel sprouting. Furthermore, isomangiferin treatment inhibited VEGF-induced proliferation of human umbilical vein endothelial cells and the formation of capillary-like structures. Mechanistically, isomangiferin induced caspase-dependent apoptosis of breast cancer cells. Furthermore, VEGF-induced activation of the VEGFR-2 kinase pathway was down-regulated by isomangiferin.

Conclusion

Our findings demonstrate that isomangiferin exerts anti-breast cancer effects via the functional inhibition of VEGFR-2. Pharmaceutically targeting VEGFR-2 by isomangiferin could be an effective therapeutic strategy for breast cancer.

Immunoglobulin-like domain 4-mediated ligand-independent dimerization triggers VEGFR-2 activation in HUVECs and VEGFR2-positive breast cancer cells

PURPOSE

The extracellular region (EC) of the vascular endothelial growth factor (VEGF) receptor-2 (VEGFR-2) contains seven immunoglobulin-like (Ig-like) domains that are required for specific ligand binding and receptor dimerization. Studies of domain 4-7 deletions and substitutions provided insights into the interaction between receptors in the absence of VEGF. In this study, we investigated the effect of domain 4 in ligand-independent VEGFR-2 dimerization and activation in human vascular endothelial cells and human breast cancer cells.

METHODS

To confirm the role of domain 4 in ligand-independent receptor dimerization and activation, two VEGFR-2 fragments with and without domain 4, KFP1 and KFP2, were generated by recombinant DNA technology. We measured the affinity of KFP1 and KFP2 with VEGFR-2, and the roles of KFP1 and FKP2 in dimerization and phosphorylation of VEGFR-2. We also evaluated the effect of KFP1 and FKP2 on cell proliferation and migration in HUVECs and in human breast cancer cells.

RESULTS

We showed that KFP1 did not affect the interaction of VEGFR-2 and VEGF but bound VEGFR-2 in the absence of VEGF. Furthermore, cross-linking and cross-linking immunoblotting demonstrated that KFP1 could form a complex with VEGFR-2, which resulted in VEGFR-2 dimerization in the absence of VEGF. Importantly, we found that the KDR fragment with domain 4 induced phosphorylation of VEGFR-2, as well as phosphorylation of downstream receptor kinases in HUVECs and VEGFR-2-positive breast cancer cells. Consistent with these results, this ligand-independent activation of VEGFR-2 also promoted downstream signaling and cell proliferation and migration.

CONCLUSIONS

The domain 4 of VEGFR-2 plays an important role in the interaction between VEGFR receptors in the absence of VEGF.

Vascular endothelial growth factor receptor isoforms: are they present in oral squamous cell carcinoma?

PURPOSE

Although the clinical importance of vascular endothelial growth factor (VEGF) overexpression in oral squamous cell carcinoma (OSCC) has been investigated, there are limited data about the overexpression of VEGF receptors (VEGF-Rs) and their clinical importance. VEGF-R isoforms have proven influence on proliferation rates, metastasis, and survival in different neoplasms. This study was conducted to investigate VEGF-R expression levels in OSCC samples and to identify any clinical relevance.

MATERIALS AND METHODS

A retrospective cohort study design (n = 50) was used. Clinical data were gathered from patient charts. Validated immunohistochemical methods were applied to determine VEGF-R isoform expression by tumor cells. Descriptive and inferential statistics with respect to the variable scale were computed. The significance level was set at a P value less than or equal to .05.

RESULTS

This study found overexpression of different VEGF-R isoforms in 88% of examined specimens. Statistically important associations were detected between overexpression of specific VEGF-Rs and tumor size, neck node metastasis, and tumor-associated death. Furthermore, a history of common OSCC risk factors (smoking and alcohol consumption) were found considerably more often in patients whose OSCC specimens displayed VEGF-R overexpression.

CONCLUSION

These findings show that VEGF-R overexpression occurs frequently in OSCC and could have clinical implications.

VEGF targets the tumour cell

The function of vascular endothelial growth factor (VEGF) in cancer is not limited to angiogenesis and vascular permeability. VEGF-mediated signalling occurs in tumour cells, and this signalling contributes to key aspects of tumorigenesis, including the function of cancer stem cells and tumour initiation. In addition to VEGF receptor tyrosine kinases, the neuropilins are crucial for mediating the effects of VEGF on tumour cells, primarily because of their ability to regulate the function and the trafficking of growth factor receptors and integrins. This has important implications for our understanding of tumour biology and for the development of more effective therapeutic approaches.

Evaluation of tyrosine receptor kinases in the interactions of head and neck squamous cell carcinoma cells and fibroblasts

OBJECTIVE

Despite treatment advancements, disease-free survival of head and neck squamous cell carcinoma (HNSCC) has not significantly improved. This may be a result of tumor-fibroblasts interactions providing protective pathways for oncogenic cells to resist therapy. Further understanding of these relationships in HNSCC may improve effectiveness of targeted therapies. In this article, we investigated the role of several receptor tyrosine kinases (RTKs) in the interactions between HNSCC cells and supporting cells (fibroblasts).

MATERIALS AND METHODS

HNSCC cell lines and human tumor samples were evaluated for FGFR1/2/3, and PDGF-beta expression levels. Cell lines (FADU, SCC1, OSC19, Cal27, SCC22A) were treated with a range of physiological concentrations of dovitinib and assessed for proliferation, cytotoxicity, and apoptosis. Mice bearing HNSCC xenografts were treated with dovitinib (20 mg/kg).

RESULTS

Evaluation of HNSCC tumor specimens, cell lines and fibroblasts found variable expression of multiple RTKs (fibroblasts growth factor receptor, platelet derived growth factor receptor and vascular endothelial growth factor receptor) and their ligands, supporting previous theories of paracrine and autocrine signaling within the microenvironment. In a dose-dependent fashion, RTK inhibition reduced proliferation of HNSCC cell lines and fibroblast in vitro. When HNSCC cells were cocultured with fibroblasts, RTK inhibition resulted in a smaller reduction in the proliferation relative to untreated conditions. In vivo, RTK inhibition resulted in significant tumor regression and growth inhibition (p<0.05) and reduced the incidence of regional lymph node metastasis.

CONCLUSION

Effective treatment of HNSCC, therefore, may require inhibition of multiple RTKs in order to adequately inhibit the microenvironment's various signaling pathways.

Vascular endothelial growth factor receptor 2 as a marker for malignant vascular tumors and mesothelioma: an immunohistochemical study of 262 vascular endothelial and 1640 nonvascular tumors

Vascular endothelial growth factor receptor 2 (VEGFR2) is a primary responder to vascular endothelial growth factor signal and thereby regulates endothelial migration and proliferation. This receptor is expressed in endothelial cells and in some vascular tumors, but many reports also detail its expression in carcinomas and lymphomas. VEGFR2 is a potential cell-type marker, and data on VEGFR2 expression may also have therapeutic significance in view of recent availability of VEGFR2 inhibitors. In this study, we immunohistochemically examined 262 vascular endothelial and 1640 nonvascular tumors and selected non-neoplastic tissues with a VEGFR2-specific rabbit monoclonal antibody 55B11. In early human embryo, VEFGR2 was expressed in endothelia of developing capillaries and in the thoracic duct, great vessels, hepatic sinusoids, epidermis, and mesothelia. In late first trimester fetus peripheral soft tissues, VEGFR2 was restricted to capillary endothelia, chondrocytes, and superficial portion of the epidermis. In normal adult tissues, it was restricted to endothelia and mesothelia. VEGFR2 was consistently expressed in angiosarcomas, Kaposi sarcomas, and retiform hemangioendotheliomas. It was detected in only half of epithelioid hemangioendotheliomas (15/27), usually focally. VEGFR2 was strongly expressed in most capillary hemangiomas and weakly or focally in cavernous, venous, and spindle cell hemangiomas and in lymphangiomas. Malignant epithelial mesothelioma was found to be a unique epithelial neoplasm with a strong and nearly consistent VEGFR2 expression, including membrane staining (35/38). Approximately 10% of squamous cell carcinomas and 23% of pulmonary adenocarcinomas contained focal positivity. The only nonendothelial mesenchymal tumors found to be VEGFR2 positive were biphasic synovial sarcoma (focal epithelial expression) and chordoma. All melanomas and lymphomas were negative. VEGFR2 is a promising marker for malignant vascular tumors and malignant epithelioid mesothelioma. Expression in biphasic synovial sarcoma epithelium, chordoma, and some carcinomas has to be considered in differential diagnosis. Information on VEGFR2 tissue expression may be useful in development of targeted oncologic therapy through VEGFR2-specific tyrosine kinase inhibitors.

Vascular endothelial growth factor receptor-2 in breast cancer

Investigations over the last decade have established the essential role of growth factors and their receptors during angiogenesis and carcinogenesis. The vascular endothelial growth factor receptor (VEGFR) family in mammals contains three members, VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1) and VEGFR-3 (Flt-4), which are transmembrane tyrosine kinase receptors that regulate the formation of blood and lymphatic vessels. In the early 1990s, the above VEGFR was structurally characterized by cDNA cloning. Among these three receptors, VEGFR-2 is generally recognized to have a principal role in mediating VEGF-induced responses. VEGFR-2 is considered as the earliest marker for endothelial cell development. Importantly, VEGFR-2 directly regulates tumor angiogenesis. Therefore, several inhibitors of VEGFR-2 have been developed and many of them are now in clinical trials. In addition to targeting endothelial cells, the VEGF/VEGFR-2 system works as an essential autocrine/paracrine process for cancer cell proliferation and survival. Recent studies mark the continuous and increased interest in this related, but distinct, function of VEGF/VEGFR-2 in cancer cells: the autocrine/paracrine loop. Several mechanisms regulate VEGFR-2 levels and modulate its role in tumor angiogenesis and physiologic functions, i.e.: cellular localization/trafficking, regulation of cis-elements of promoter, epigenetic regulation and signaling from Notch, cytokines/growth factors and estrogen, etc. In this review, we will focus on updated information regarding VEGFR-2 research with respect to the molecular mechanisms of VEGFR-2 regulation in human breast cancer. Investigations in the activation, function, and regulation of VEGFR-2 in breast cancer will allow the development of new pharmacological strategies aimed at directly targeting cancer cell proliferation and survival.