Immune regulation of metastasis from in vivo derived syngeneic murine melanoma.

In earlier work, we demonstrated that in vivo derived B16F10 tumor cells metastasize aggressively from intracameral (ic) and subcutanous (sc) sites, colonizing the lungs and lymph nodes. Natural killer (NK) cells play an important role in metastasis from ocular tumors. Treatment of mice with MoAb PK136, a highly specific anti-NK antibody, altered the pattern of metastasis; metastases appeared in the lungs, adrenal glands, liver, and spleen. Treatment with cyclophosphamide (Cy) did not affect survival or metastasis, but combined treatment with the immunomodulator Linomide (LS2616) and Cy decreased metastasis and increased survival. In the present study, we examine the role played by NK cells in regulating metastasis of sc tumors. Treatment of mice with LS2616 enhanced NK cell activity and decreased metastasis. Treatment with MoAb PK136 decreased survival and increased metastasis, but did not affect the pattern of metastasis. Treatment with 25 mg/kg Cy alone resulted in a decrease in growth of the primary tumor, increased survival, and decreased metastasis. Combined treatment with LS2616 and Cy was very effective in decreasing metastasis, increasing survival, and affecting cures (30%). In summary, our experiments demonstrate the importance of NK cells in regulating metastasis from sc tumors of in vivo derived B16F10 melanoma and demonstrate the effectiveness of LS2616 and low doses of Cy on metastasis and survival. In combination with earlier work, the present experiments demonstrate: 1) that modulation of NK activity differentially affects metastasis from sc and ic compartments, and 2) that regional differences in the location of the primary tumor may determine the effectiveness of treatment with Cy.