Depletion of NK cell activity results in growth of hepatic micrometastasesin a murine ocular melanoma model

Purpose. To study the role of natural killer (NK) cells in growth of sponta neous hepatic metastasis in a marine intraocular melanoma model. Methods. Tissue culture B16-LS9 melanoma cells were analyzed by flow cytome try for MHC class I expression of all haplotypes and inoculated into the po sterior compartment (PC) of one eye of C57BL6 mice. The eyes were enucleate d at 12 days post-inoculation and histologically examined for tumor growth. One group of mice (n = 10) were given intraperitoneal injections of anti-a sialo GM1 for NK cell depletion post-enucleation and a second group of mice (n = 9) served as controls. The mice were sacrificed at 24 days postinocul ation and necropsies were performed to determine the number and size of met astasis. Results. The B16-LS9 cells failed to express MHC class I antigen. Tumor gre w in the PC of all eyes and metastasized to the lungs and Livers of all mic e, with the average number of hepatic micrometastases greater in the NK dep leted group versus the control group, (p =.009). There was no significant d ifference in the average number of pulmonary metastases in the treated vers us the control group (p =.072). Hepatic metastases grew to an average diame ter of 600 mu m in diameter in two NK depleted mice. Conclusions. NK depletion in this model of metastatic ocular melanoma resul ts in increased number and growth of hepatic micrometastases.