Abstract 5410: Tim-3 expression and function in natural killer cells from metastatic melanoma patients

Abstract

Abstract BACKGROUND: Tim-3 (T-cell immunoglobulin domain and mucin domain 3) is a type-I glycoprotein receptor with pivotal roles in immune regulation and tolerance induction. Tim-3 has opposing roles in innate and adaptive immunity. It synergizes with TLR signaling in DCs inducing the production of inflammatory cytokines, while it acts as a negative regulator of Th1/Tc1 cell function by triggering T cell apoptosis upon interaction with its ligand, galectin-9. Tim-3 is also responsible for the functional exhaustion of T cells observed in some chronic infectious diseases and tumors, such as metastatic melanoma (MM). Natural Killer (NK) cells, innate immune cells which eliminate tumors and infected cells through cytotoxicity and IFNγ production, constitutively express Tim-3. Moreover, it has been described that some tumor cells (including melanoma cells) express and secrete galectin-9. However, little is known about the role of Tim-3 on NK cells, particularly in the presence of galectin-9, in healthy or melanoma patients. METHODS: Purified NK cells from PBMCs of 20 melanoma donors (MD) and 40 healthy donors (HD) were characterized according to the expression of Tim-3 by flow cytometry. Lamp-1 expression on NK cell surface was used to measure NK cell cytotoxicity against the following target cells: i) K562 cells which don't express Galectin-9 and ii) Gmel galectin-9+ and Gmel galectin-9- sorted melanoma cells. IFNγ production was assessed by intracellular staining after 4 hours culture in presence of IL-12. RESULTS: MD NK cells express higher levels of Tim-3 compared to HD NK cells (p<0.05). Moreover, MD NK cells have a defect in cytotoxicity, proliferation and IFNγ production, but it still remains unclear if Tim-3 is involved in this exhausted phenotype. So far, we found that Tim-3 expression by itself (without engagement of specific ligands) does not negatively affect NK cell cytotoxicity. However, the expression of Galectin-9 by the target cells induces a decrease in NK cell cytotoxicity (Gmel Gal-9+ vs Gmel Gal-9-). CONCLUSION: These data suggest that when engaged with Galectin-9, Tim-3 expression down-modulates NK cell cytotoxicity. Therefore, galectin-9 expression may be a possible mechanism for tumors to evade immune surveillance. Given that an increasing body of data supports an important role for Tim-3/Galectin-9 interaction in immune regulation in infectious diseases and cancer, deciphering the function of Tim-3 in different cell types will be critical for potentially targeting it therapeutically. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5410. doi:1538-7445.AM2012-5410