Cytotoxic effects of γδ T cells expanded ex vivo by a third generation bisphosphonate for cancer immunotherapy

Nitrogen containing-bisphosphonates (N-BPs), widely used to treat bone diseases, have direct antitumor effects via the inactivation of Ras proteins. In addition to the direct antitumor activities, N-BPs expand gamma delta T cells, which exhibit major histocompatibility complex-unrestricted lytic activity. Bps accumulate intermediate metabolites which may be tumor antigens in target cells. The purpose of our study was to clarify the cytotoxicity of -gamma delta T cells expanded ex vivo by the most potent N-BP, zoledronate (ZOL). Especially, we focused on the importance of pretreatment against target cells also with ZOL; 1 mu M ZOL plus IL-2 increased the absolute number of gamma delta T cells 298-768 fold for 14 days incubation. The small cell lung cancer and fibrosarcoma cell lines pretreated with 5 mu M ZOL showed a marked increase in sensitivity to lysis by gamma delta T cells. While, untreated cell lines were much less sensitive to lysis by gamma delta T cells. Video microscopy clearly demonstrated that gamma delta T cells killed target cells pre-treated with ZOL within 3 hr. Pretreatment with 80 mu g/kg ZOL also significantly enhanced the antitumor activity of gamma delta T cells in mice xenografted with SBC-5 cells. These findings show that ZOL significantly stimulated the proliferation of gamma delta T cells and that gamma delta T cells required pre-treatment with ZOL for cytotoxic activity against target cells. (c) 2005 Wiley-Liss, Inc.