Bevacizumab for the Control of Uveal Melanoma in vitro and in vivo

Abstract

Purpose: : Tumors release vascular endothelial growth factor (VEGF) protein causing angiogenesis, which is essntial to tumor growth and metastasis. Recent studies have shown that blocking VEGF may inhibit the growth of non-small cell lung, breast and colorectal carcinomas and their metastases. The purpose of this study is to determine whether anti-VEGF therapy is able to inhibit the growth of primary uveal melanoma in vitro and in vivo and hepatic micrometastasis in vivo.

Methods: : Human uveal melanoma cell lines Mel290, Mel270, 02-1486 and HUVEC, and mouse B16LS9 and vascular endothelium were separately cultured or co-cultured and incubated with bevacizumab. The level of VEGF protein in the culture media was measured by VEGF ELISA and cell viability with a Hoechst 33258 assay. B16LS9 melanoma cells were inoculated into the posterior chamber of the right eyes of 12-week old female C57Bl/6 mice, and eyes were enucleated after 7 days. The sizes of the intraocular tumors were determined with Image J. Intraperitoneal injections of bevacizumab were started on the 4^th day after inoculation and repeated twice weekly for 4 weeks. The mice were divided into 3 groups: group 1: 50µg of bevacizumab, group 2: 250µg of bevacizumab, group 3: an equal volume of PBS as a control. Livers were collected after 28^th days and hepatic micrometastases were counted. For longitudinal observation, hepatic tissue was collected at 1, 2, 3, 4 or 6 weeks after inoculation.

Results: : 24 hours after incubation of tumor cells or tumor cells cocultured with vascular endothelium with bevacizumab, the level of VEGF was significantly reduced in all cell cultures, while the viability of human uveal melanoma and mouse B16LS9 cells was decreased, also after co-culture with vascular endothelium. The size of intraocular B16LS9 was decreased in both the 50µg (P=0.02) and the 250µg (P=0.01) bevacizumab groups compared to controls. The number of hepatic micrometastasis was lower in both the 50µg (P=0.013) as well as the 250µg (P=0.0016) bevacizumab group compared with the controls.

Conclusions: : Treatment with bevacizumab suppressed the in vitro and in vivo growth and the development of hepatic micrometastasis of melanoma cells. Bevacizumab is a potential therapeutic agent for the treatment of primary uveal melanoma and its metastasis.

Keywords: melanoma • uvea • vascular endothelial growth factor