Abstract
Purpose:
The influence of VEGF and its potential inhibitory impact on uveal melanoma (UM) cell growth is controversial. In this study, we investigated the effect of the VEGF isoforms VEGF165 (pro-angiogenic) and VEGF165b (anti-angiogenic) as well as of VEGF-antagonist bevacizumab on UM cells.
Methods:
Five UM cell lines were used, derived from both primary tumors (92.1, Mel 270) and metastases (OMM2.5, OMM2.3, OMM1). Secretion of VEGF-A was evaluated in ELISA. Influence of 10 ng/ml and 100 ng/ml VEGF165 and VEGF165b, respectively, on UM cells was assessed. Proliferation and toxicity was assessed by WST assay, cell migration using a scratch assay. Cell death was induced by hydrogen peroxide. The expression and phosphorylation of the mitogen activated kinase, Erk1/2, and the expression of the apoptosis-related proteins, Bax and Bcl2, were evaluated in Western blots.
Results:
All evaluated cell lines secreted VEGF-A. Application of VEGF165 resulted in a significant reduction in cell proliferation in all lines, while VEGF165b only displayed minimal (but significant) reducing effects on the proliferation of OMM1 and OMM2.3. The application of bevacizumab (250µg/ml) had no effect. VEGF165 and VEGF165b were able to accelerate wound healing in OMM1 cells; however, they displayed a slight decelerating effect in OMM2.3 cells, with VEGF165 additionally having some effect on both OMM2.5 and Mel270 cells. Bevacizumab again displayed no effect in either cell line. In Mel270 cells, VEGF165 and VEGF165b reduced the Bax/Bcl2 ratio.<br /> The susceptibility of UM cells to hydrogen peroxide-induced cell death varied. In all cell lines, VEGF165 protected cells from hydrogen peroxide-induced cell death; however bevacizumab was also protective. We found that in Mel 270 cell line, bevacizumab increased the pErk/Erk ratio.
Conclusions:
The inconsistent effect of VEGF and VEGF inhibition found in the literature can be supported by these results. VEGF was able to protect UM cells from oxidative stress-induced cell death, but, contrary to expectations, proangiogenic VEGF inhibited the proliferation rate of UM cells, while the effect of VEGF and VEGF165b on wound healing was cell line dependent. Bevacizumab, on the other hand, protected UM cells from oxidative stress-induced cell death. These data indicate that a therapy targeting VEGF only in UM is not likely to be beneficial to patients.