Orthotopic human choroidal melanoma xenografts in nude rats with aggressive and nonaggressive PAS staining patterns.

PURPOSE Choroidal melanoma is the most common primary ocular cancer among the adult population. Patient survival has been linked to the periodic acid-Schiff base (PAS)-positive vascular patterns in the tumors. The presence of PAS-positive loops or cross-linking parallel channels is a marker of an aggressive tumor. The purpose of this study was to develop new xenograft models of human choroidal melanoma that predictably demonstrate the PAS staining patterns associated with nonaggressive and aggressive tumors in humans. METHODS Three human choroidal melanoma cell lines (C918, M619, and OCM-1) were used. C918 and M619 are considered aggressive, based on their ability to form PAS-positive channels in vitro. The nonaggressive OCM-1 cells do not form these channels. C918, M619, and OCM-1 spheroids were grown and implanted in the suprachoroidal space of 20, 17, and 16 WAG/RijHs-rnu nude rats, respectively. Tumors were grown for 1 to >4 weeks, and histology was performed to evaluate tumor growth and determine PAS labeling patterns. RESULTS Growth of C918, M619, and OCM-1 xenografts were histologically verified in 20/20, 15/17, and 16/16 rats, respectively. PAS staining revealed loops and cross-linking parallel channels, typical of aggressive tumors in patients, in 90% of C918 and 100% of M619 xenografts. Only 4 of 16 OCM-1 xenografts showed PAS-positive loops. The rest showed no PAS staining or only perivascular staining, indicative of nonaggressive tumors. CONCLUSIONS It is possible to grow human choroidal melanoma orthotopic xenografts in nude rats that reproduce the PAS staining patterns associated with aggressive and nonaggressive choroidal melanomas in patients.