MC-38 adenocarcinoma tumor infiltrating lymphocytes: Correlation of cytotoxicity with time of tumor harvest after tumor inoculation

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Abstract
Tumor infiltrating lymphocytes (TILs) are capable of mediating significant tumor regressions in vitro and in vivo in animal systems. In humans, however, many TIL cell lines are not cytotoxic in vitro, and clinical trials thus far have been less than encouraging. We attempted to correlate TIL cytotoxicity with time of tumor harvest and TIL cell surface antigenic expression. TILs harvested from early MC‐38 adenocarcinoma tumors (days 9 and 20 post‐tumor implantation), demonstrated significantly higher cytotoxicity against a variety of tumor targets compared to older TILs (days 31 and 37), The younger TILs had a higher expression of the Lyt‐1 (Helper T cells), asialo GM1 (NK and T cells), and 49H.8 (NK cells) antigens. Comparison with the MCA‐102 sarcoma, a tumor that does not lead to cytotoxic TILs, revealed a low expression of the Lyt‐1 antigen on their cell surface. We conclude that TILs cytotoxicitv is time‐dependent and may be dependent on the presence of Lyt‐1+ cells in the overall TIL population of cells.