Determination of Melanoma Inhibitory Activity (MIA) Levels in an Animal Model of Uveal and Cutaneous Melanoma

Abstract

Abstract: : Purpose: Melanoma inhibitory activity (MIA) is a protein expressed by primary and metastatic melanoma cells. Several clinical studies have suggested that increasing serum levels of MIA correlates with metastatic disease in cutaneous melanoma (CM) and uveal melanoma (UM). Therefore MIA levels may be a useful tool in the follow–up of melanoma patients both in monitoring their response to therapy and detecting early recurrent and metastatic disease. We have previously reported CM and UM rabbit models. The aim of this study is to compare the MIA serum levels in immunosuppressed rabbits inoculated with CM or UM cell lines. Methods: The UM and CM immunosuppressed rabbit models were performed as previously reported by The Henry C. Witelson Ocular Pathology Laboratory, McGill University, Montreal, Canada. Blood samples from ten albino rabbits (five with CM intraocular tumors and five with UM intraocular tumors) were collected once a week from the 7^th, 8^th, 10^th, 11^th, 12^th weeks. MIA serum levels were measured by a one–step ELISA as previously described. Results: The mean MIA serum levels in the UM rabbits were 1.17, 1.70, 1.60, 1.48, 1.37 ng in the 7^th, 8^th, 10^th, 11^th, 12^th weeks respectively. There was no statistically significant difference between the weekly serum levels. In comparison, the mean MIA serum levels in the CM rabbits were 4.08, 4.36, 5.09, 4.49, 5.50 ng in the 7^th, 8^th, 10^th, 11^th, 12^th weeks respectively. Statistical analysis showed a highly significant difference (p < 0.015) between the mean MIA serum levels in the UM and CM rabbit plasma during the weeks of this experiment. Conclusions: The MIA serum levels differed significantly between the two types of melanoma in these animal models, with average CM serum levels of MIA measuring three times higher than those of UM. The difference observed in MIA expression may be related to the higher metastatic potential of skin melanoma cells compared to uveal melanoma cells. The absence of a significant increase in MIA levels throughout the progression of the experiment for each cell line may be attributed to the fact that all rabbits during this time frame had already developed metastases.

Keywords: melanoma • pathology: experimental