IMMUNE PARAMETERS OF MICE BEARING HUMAN HEAD AND NECK-CANCER

A xenogeneic human head and neck squamous cell carcinoma (HNSCC) model in immunocompatent mice was evaluated for its requirement of cyclosporine for progressive tumor growth. Tumor growth and T cell functions were assessed in mice receiving cyclosporine treatment for various lengths of time. Tumor cells were injected s.c. on day 1 and cyclosporine was injected i.p. daily on days 1, 1-7, 1-14, 1-21, or for the entire 28 days of tumor growth. All mice developed tumors. These tumors were confirmed to be squamous carcinomas of human origin histologically and by positive staining for human MHC class I antigen expression. Tumors were largest in mice that received cyclosporine for days 1-21 or days 1-28. Increased tumor size was associated with increased serum levels of tumor-reactive antibodies, an increased intratumoral frequency of CD4(+) and CD8(+) cells, but a diminished production of interleukin-2 (IL-2) by the tumor infiltrate. Also correlating with increasing tumor size was splenomegaly, a decline in the frequency, but not the absolute levels, of splenic CD4(+) and CD8(+) cells, and a diminished capacity to proliferate in response to concanavalin A and to be stimulated to secrete IL-2. The HNSCC tumors contributed to the immune decline since T cell functions were more depressed in the tumor bearers than in control mice receiving only cyclosporine treatment. These results demonstrate that human HNSCC tumor xenografts can grow in mice even with limited cyclosporine treatment, and that the survival of these xenografts may, in part, be due to a tumor-induced decline in select T cell functions.