652. Culture and Characterization of Tumor-Infiltrating Lymphocytes of the Syrian Hamster

Abstract

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) has developed into a promising treatment modality for metastatic cancer. However, preclinical animal models for studying TIL therapy are limited to mice and therefore we set out to culture and characterize TIL from another rodent species, the Syrian hamster. First, we examined the presence of CD4+ and CD8+ cells in six implantable syngeneic hamster tumors representing various histologies. A tumor type-dependent pattern of lymphocyte infiltration was observed, with CD8+ cells ranging from 0.08% to 0.93% (of all tumor cells) and CD4+ cells ranging from 0.17% to 3.25%. To establish TIL cultures, excised tumor fragments were cultured in high-dose human interleukin-2 (IL-2) for 10 days. Flow cytometric analyses of Day 10 TIL cultures revealed a predominance of CD4+ cells over CD8+ cells in all tumor types studied. In effector/target assays the TIL cultured from HapT1 (pancreatic adenocarcinoma) and RPMI 1846 (melanoma) exhibited tumor-specific cytolytic activity. In addition, MHC Class I blocking abrogated the cell killing of RPMI 1846 TIL, suggesting that cytotoxic CD8+ T-cells were responsible for the observed cytolytic activity. Only partial abrogation was seen with HapT1 TIL suggesting the presence of cytotoxic CD4+ T-cells in the TIL population, which is supported by the observation that HapT1 tumor cells express MHC Class II. To our knowledge, this is the first time tumor-infiltrating lymphocytes of the Syrian hamster have been cultured and characterized. Thorough immunophenotyping of hamster tumors and TIL cultures requires the development of new hamster-specific antibodies in addition to the currently available ones used in this study. In conclusion, our data supports the use of the Syrian hamster as a novel platform for testing TIL protocols in a species other than mouse or human.