Local interleukin-2 therapy in bovine ocular squamous cell carcinoma. A pilot study.

Five cows bearing bovine ocular squamous cell carcinoma (BOSCC) were treated with low doses of recombinant human interleukin-2 (rhIL-2). A dose of 2500 U rhIL-2 was injected intralesionally and another 2500 U were injected into the subparotid regional lymph node once a day during a period of 5 consecutive days. This cycle of 5 days was repeated after an interval of 2 days. Total regression of the tumor was observed in three out of five animals. One cow showed tumor regression (greater than 80%) accompanied by metastases to the regional lymph node that were observed from the fifth week after the beginning of the treatment. Growth of the tumor of the fifth animal was retarded after treatment. In vitro proliferation of peripheral blood lymphocytes was investigated in two animals and tumor-infiltrating lymphocytes in one animal during incubation in various rhIL-2 concentrations. Cytotoxic activity of both cell populations against P815, Yac-1 and BOSCC-derived cell lines increased during incubation with rhIL-2. Cultured BOSCC-infiltrating lymphocytes showed predominant killing of the BOSCC-derived autologous cell line after 4 weeks of culture. Preliminary phenotype analysis did not give conclusive results with respect to the types of cells responsible for killing.