Purpose: The expression of CD56, a natural killer cell - associated molecule, on αβ T lymphocytes correlates with their increased antitumor effector function. CD56 is also expressed on a subset of γδ T cells. However, antitumor effector functions of CD56 + γδ Tcells are poorly characterized. Experimental Design: To investigate the potential effector role of CD56+ γδ Tcells in tumor killing, we used isopentenyl pyrophosphate and interleukin-2- expanded γδ T cells from peripheral blood mononuclear cells of healthy donors. Results: Thirty to 70% of expanded γδ Tcells express CD56 on their surface. Interestingly, although both CD56 + and CD56- γδ Tcells express comparable levels of receptors involved in the regulation of γδ T-cell cytotoxicity (e.g., NKG2D and CD94), only CD56+ γδ T lymphocytes are capable of killing squamous cell carcinoma and other solid tumor cell lines. This effect is likely mediated by the enhanced release of cytolytic granules because CD56+ γδ T lymphocytes expressed higher levels of CD107a compared with CD56- controls following exposure to tumor cell lines. Lysis of tumor cell lines is blocked by concanamycin A and a combination of anti-γδ T-cell receptor + anti-NKG2D monoclonal antibody, suggesting that the lytic activity of CD56+ γδ Tcells involves the perforin-granzyme pathway and is mainly γδT-cell receptor/NKG2D dependent. Importantly, CD56-expressing γδT lymphocytes are resistant to Fas ligand and chemically induced apoptosis. Conclusions: Our data indicate that CD56+ γδ Tcells are potent antitumor effectors capable of killing squamous cell carcinoma and may play an important therapeutic role in patients with head and neck cancer and other malignancies.
ASJC Scopus subject areas
- Cancer Research