Natural killer cell tumoricidal activity and deterioration of lung tumor metastasis in silicotic mice and stressed silicotic mice

Aim of this study is to explore the role of splenic NK cells in the lung metastasis in the silicotic mice. The number of metastatic foci increased 1.5-fold and 1.8-fold in the silicotic and stressed silicotic mice compared with the control mice. Treatment with an immunomodulator reduced the rate of tumor metastasis in silicotic mice with or without stresses, while their NK cell activity was normalized. Decrease of NK cell activity on the day of tumor inoculation but not on the post-inoculation days seems to be a major factor for predicting the extent of tumor metastasis in the silicotic and stressed silicotic mice.