VEGF Potentiates GD3-Mediated Immunosuppression by Human Ovarian Cancer Cells

Abstract

Purpose Natural killer T (NKT) cells are important mediators of anti-tumor immune responses. We have previously shown that ovarian cancers shed the ganglioside GD3, which inhibits NKT cell activation. Ovarian cancers also secrete high levels of vascular endothelial growth factor (VEGF). In this study, we sought to test the hypothesis that VEGF production by ovarian cancers suppresses NKT cell-mediated anti-tumor responses. Experimental Design To investigate the effects of VEGF on CD1d-mediated NKT cell activation, a conditioned media model was established wherein the supernatants from ovarian cancer cell lines (OV-CAR-3 and SK-OV-3) were used to treat CD1d-expressing antigen presenting cells (APC) and co-cultured with NKT hybridomas. Ovarian cancer associated-VEGF was inhibited by treatment with Bevacizumab and Genistein, conditioned medium was collected and CD1d-mediated NKT cell responses were assayed by ELISA. Results Ovarian cancer tissue and ascites contain lymphocytic infiltrates, suggesting that immune cells traffic to tumors, but are then inhibited by immunosuppressive molecules within the tumor microenvironment. OV-CAR-3 and SK-OV-3 cell lines produce high levels of VEGF and GD3. Pretreatment of antigen presenting cells with ascites or conditioned medium from OV-CAR-3 and SK-OV-3 blocked CD1d-mediated NKT cell activation. Inhibition of VEGF resulted in a concomitant reduction in GD3 levels and restoration of NKT cell responses. Conclusions We found that VEGF inhibition restores NKT cell function in an in-vitro ovarian cancer model. These studies suggest that the combination of immune modulation with anti-angiogenic treatment has therapeutic potential in ovarian cancer.

The Angiogenic Secretome in VEGF overexpressing Breast Cancer Xenografts

“…Consistent with our observations that TIMP-1 significantly increased in TIF with VEGF overexpression in MCF-7 tumors, exogenous VEGF administration has been associated with TIMP-1 release in the retina40, although the regulation of TIMP-1 by VEGF is not fully understood. TIMP-1 is known to play a role in inflammation and immunity41, and its increase with VEGF overexpression is consistent with observations that VEGF potentiates immune suppression42.…”

Anti-tumour activity of tivozanib, a pan-inhibitor of VEGF receptors, in therapy-resistant ovarian carcinoma cells

“…Spannuth et al have demonstrated higher expression of VEGFR2 in malignant ovarian samples compared to benign or borderline tumours, which showed a correlation with tumour grade and aggressiveness3952. Moreover, VEGFA suppresses immune-mediated anti-tumour responses in EOC53. Although these findings indicate that the VEGF/VEGFR loop promotes malignant progression in EOC, the role of this pathway in driving the chemoresistant disease is largely unknown.…”

Targeted attack: mechanisms by which ovarian cancers suppress the immune system

“…discuss our recent findings (8) and provide insight into potential future directions. The impact of angiogenic factors on the tumor microenvironment, reported by Bamias and Gavalas, underscore the effects of VEGF on immune cell responses.…”

“…It has been well established that evading immune surveillance is critical for tumor growth and metastasis, and other groups have shown that vascular endothelial growth factor (VEGF) expression is inversely correlated with survival in ovarian cancer patients (6,7). Therefore, we investigated the effects of ovarian cancer-associated VEGF on CD1d-mediated antigen presentation to natural killer T (NKT) cells (8). We found that inhibition of VEGF production by ovarian cancer cell lines led to a reduction in the expression of the immunosuppressive ganglioside GD3 and restored NKT cell activation.…”