Abstract 359: Insulin-like growth factor 1 receptor (IGF-1R) as a target for treatment of metastatic uveal melanoma

Abstract

Abstract Uveal melanoma is the most common primary intraocular malignant tumor in adults; 30% to 50% of patients ultimately succumb to metastatic disease, predominantly to hepatic metastasis. Despite new diagnostic and therapeutic tools, the survival rate for patients with metastatic uveal melanoma remains poor. The reason for the hepato-tropism of metastatic uveal melanoma is largely unknown. It has been reported that the type 1 insulin-like growth factor receptor (IGF-1R) is expressed in more than 70% of primary uveal melanoma tissue specimens; expression of IGF-1R is correlated to poor prognosis. IGF-1 which binds to IGF-1R is produced mainly in the liver and this may account for the hepato-tropism of uveal melanoma. In this study, we investigated the effect of IGF-1 on the in vitro growth of metastatic uveal melanoma cells. The expression of IGF-1R on a metastatic uveal melanoma cell line (UM001), established from a hepatic metastasis, was demonstrated by flow cytometry and western blot analyses. The effect of IGF-1 on tumor-cell growth was then tested by adding IGF-1 (R&D Systems, Minneapolis, MN) to the culture wells of UM001 cells with serum-free medium (SFM) containing RPMI 1640 supplemented with 50 μg/ml transferrin and 0.1% bovine serum albumin. MTT and BrdU assays were used to measure proliferative activity. Furthermore, anti-IGF-1R antibody (MAB391; R&D Systems) was added to a serum-containing culture medium to investigate the role of IGF-1 on the growth of metastatic uveal melanoma cells. IGF-1R negative (R-) and positive (R600) cell lines were used as controls in our experiments. The R- cell line was derived from a 3T3-like fibroblasts isolated from mouse embryos with a targeted disruption of the IGF-IR gene (IGF-1R negative). The R600 cell line is a stable cell line which was derived from the R- cell line and expresses 30,000 molecules of human IGF-IR/cell. Flow cytometric analysis showed that UM001 cells express IGF-1R on their surface (>90%). In western blotting analysis, UM001 cells have approximately 11,700 molecules of human IGF-IR/cell. In proliferation assays, UM001 cells in SFM were exposed to IGF-I in concentration ranging from 0 to 300 ng/ml for 72 hours. The UM001 cells proliferated in response to exogenous IGF-1 and increased BrdU uptake by 49.1% at IGF-1 level of 300 ng/ml compared to 0 ng/ml (p=0.039). In a blocking assay, UM001 cells were cultured for 24 hours in RPMI 1640 medium supplemented with 10% fetal bovine serum and antibody against either IGF-1R (30 μg/ml) or mouse IgG1 as an isotope control. We found that 30 μg/ml of anti-IGF-1R antibody blocks the proliferative activity of UM001 cells by 70%. These results suggest that IGF-1 is an important growth factor for metastatic uveal melanoma cells. Further investigation on the efficacy of IGF-1R blockade on the growth of metastatic uveal melanoma may open a new treatment approach for this disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 359.