Tumor infiltrating lymphocytes: CD8+lymphocytes in canine transmissible venereal sarcomas at different stages of tumor growth

This study utilized an in vivo tumor system(canine transmissible venereal sarcoma, CTVS) to assess wh correlation exists between tumor growth stage and phenotype of infiltrating lymphocytes. Additionally, the ability:of CTVS cells to produce chemoattractants for canine lymphocytes was assessed The CD8 subset of tumor infiltrating lymphocytes (TIL) during progressive growth, steady-state (no growth), and regression of the CTVS was determined During progressive growth, the proportion of TIL expressing CD8 was significantly lower than that from regressing tumors (P < .001) and steady-state tumors (P < .01). Additionally, CTVS cell culture, CTVS spheroid cell culture, and CTVS spheroid/canine lymphocyte co-culture supernatants were tested for chemotactic activity for canine lymphocytes. CTVS and CTVS spheroid/canine lymphocyte co-culture supernatants both had significant chemotactic activity. Conversely, CTVS spheroid culture supernatants were negative for chemotactic activity for canine lymphocytes. These results indicate a correlation exists between the CD8 subset of TIL and clinical stage of the tumor. Also, we have shown that CTVS cells in vitro produce soluble factors that cause chemotaxis of canine lymphocytes. An understanding of the role of TIL and the ability of the tumor to attract them will be of help in designing strategies;Sor immunomodulatory therapies for solid tumors.