The Invasive Properties of Uveal Melanoma Cell Lines and Their Response to Interleukin-6 (IL-6) and Vascular Endothelial Growth Factor (VEGF)

Abstract

Abstract: : Purpose: The invasive ability of tumor cells is essential to the development of metastasis. Uveal melanoma cell lines have been shown to express cytokines, such as IL-6 and VEGF, which may affect their invasive ability. This project investigated the invasive potential of uveal melanoma cell lines, and the invasive response of these cell lines to IL-6 and VEGF. Methods: The invasive properties of four uveal melanoma cell lines (92.1, MKT-BR, OCM-1, SP6.5) and one transformed melanocyte cell line (UW-1) were investigated. The invasion assay was performed with a modified Boyden chamber system consisting of a membrane with 8 µm pores pre-coated with Matrigel, an artificial basement membrane. 1x10⁵ cells were seeded onto the top portion of the chamber, with 10% FBS as a chemo-attractant in the bottom portion of the chamber. Chambers were incubated for 48 hours. The invasion assay was repeated using IL-6 and VEGF as chemo-attractants at concentrations of 10 ng/ml and 20 ng/ml respectively. Uveal melanoma cell lines have previously been reported to produce these concentrations of cytokines. Non-invading cells were removed from the top of the Matrigel, the membrane was stained and invading cells were counted under twenty high-power fields. All experiments were performed in triplicate. Results:The average invasive ability of cells without the addition of IL-6 or VEGF varied from a high level of 19.6 cells for OCM-1 to a low level of 7 cells for UW-1 and was ranked as OCM-1>92.1=SP6.5>MKT-BR>UW-1. VEGF produced at least a three-fold increase in the invasion of all uveal melanoma cell lines but had no effect on the melanocyte cell line UW-1. The addition of IL-6 produced a two-fold increase in invasion of 92.1, SP6.5 and MKT-BR, while inhibiting the invasion of OCM-1 and UW-1. Conclusions: Different uveal melanoma cell lines have different invasive potentials. In this study VEGF has been proven to be a more potent stimulant than IL-6 to the invasion of uveal melanoma cells. IL-6 has a varying effect on these cells as it stimulates invasion in three of the uveal melanoma cell lines, while inhibiting invasion in the other two. Different cytokines present in uveal melanoma may have varying effects on the invasive properties of different tumor cell populations.

Keywords: melanoma • oncology • cytokines/chemokines