Abstract 2815: Expression of insulin-like growth factor-1 receptor in metastatic uveal melanoma and implications for potential autocrine and paracrine tumor cell growth.

Abstract

Abstract Background: The survival of patients with metastatic uveal melanoma remains poor; most patients ultimately die of hepatic metastasis. Tumor cell expression of insulin-like growth factor-I receptor (IGF-1R) is a marker of poor prognosis in primary uveal melanoma. IGF-1 is produced mainly in the liver, which may account for the hepatic tropism of uveal melanoma. Therefore, we investigated the importance of IGF-1/IGF-1R interaction in hepatic metastases. Methods: The expression pattern of IGF-1R in hepatic metastases of uveal melanoma was analyzed by immunohistochemistry in a series of archival samples from patients treated at Thomas Jefferson University Hospital. To investigate the biological role of exogenous and endogenous IGF-1 on the growth of a uveal melanoma, a long-term, cell line obtained from a hepatic metastasis (TJU-UM001) was evaluated concurrently. Results: All 24 metastases stained positive by IGF-1R. Tumors showed 80-95% of cellular staining while adjacent normal liver showed negative staining. IGF-1R was expressed in both the cytoplasm and the exterior membrane of uveal melanoma cells. As previously reported (AACR 2010, Abstract #359), more than 90% of TJU-UM001 cells expressed IGF-1R on their surface and did so at approximately 1.2 x 104 IGF-1R per TJU-UM001 cell. The cell proliferation assay (Quick Cell Proliferation Assay Kit II; BioVision, Mountain View, CA) showed that quiescent TJU-UM001 was induced to proliferate by 2.6-fold (p<0.001) in response to exogenous IGF-1 at 300 ng/ml. Conversely, anti-IGF-1R antibody completely blocked the exogenous IGF-1-induced growth of TJU-UM001. IGF-1 preferentially induced phosphorylation of Akt (S473) in quiescent TJU-UM001 cells and this was blocked by anti-IGF-1R antibody. Cell proliferation kinetics analysis showed TJU-UM001 grows briskly in serum-free medium (SFM) and anti-IGF-1R antibody significantly inhibited growth. Correspondingly, TJU-UM001 maintained in SFM expressed mRNA for IGF-1 and furthermore secreted IGF-1 protein. Both anti-IGF-1 and anti-IGF-1R antibodies independently inhibited the spontaneous proliferation of the cells in SFM (p<0.05) suggesting a critical role for endogenous IGF-1 expressed by TJU-UM001 cells. Conclusion: Although the strong and extensive expression of IGF-1R in archival tissue specimens suggests paracrine stimulation via IGF-1R as a major mechanism of the growth of uveal melanoma in the liver, cell proliferation in SFM and the endogenous production of IGF-1 by tumor cells indicate an autocrine mechanism via IGF-1R is also operative. The results underscore a key role of IGF-1 in promoting the growth of uveal melanoma. The present study shows autocrine and paracrine mechanisms underlay IGF-1-induced uveal melanoma growth and indicate how these mechanisms can be targeted to suppress metastatic growth and improve clinical outcome. Citation Format: Makoto Yoshida, Senthamil Selvan, Peter A. McCue, Tiziana DeAngelis, Ami Fujii, Hallgeir Rui, Renato Baserga, Michael Mastrangelo, Takami Sato. Expression of insulin-like growth factor-1 receptor in metastatic uveal melanoma and implications for potential autocrine and paracrine tumor cell growth. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2815. doi:10.1158/1538-7445.AM2013-2815