Activating and expanding T cells using T-cell receptor (TCR) cross-linking antibodies and interleukin 2 (IL-2) results in potent cytotoxic effector cells capable of recognizing a broad range of malignant cell targets, including autologous leukemic cells. The mechanism of target cell recognition has previously been unknown. Recent studies show that ligation of NKG2D on natural killer (NK) cells directly induces cytotoxicity, whereas on T cells it costimulates TCR signaling. Here we demonstrate that NKG2D expression is up-regulated upon activation and expansion of human CD8+ T cells. Antibody blocking, redirected cytolysis, and small interfering RNA (siRNA) studies using purified CD8+ T cells demonstrate that cytotoxicity against malignant target cells occurs through NKG2D-mediated recognition and signaling and not through the TCR. Activated and expanded CD8+ T cells develop cytotoxicity after 10 to 14 days of culture, coincident with the expression of the adapter protein DAP10. T cells activated and expanded in low (30 U/mL) and high (300 U/mL) concentrations of IL-2 both up-regulated NKG2D expression equally, but only cells cultured in high-dose IL-2 expressed DAP10 and were cytotoxic. Collectively these results establish that NKG2D triggering accounts for the majority of major histocompatibility complex (MHC)-unrestricted cytotoxicity of activated and expanded CD8+ T cells, likely through DAP10-mediated signaling.

Purpose: To identify novel treatments for pediatric solid tumors and/or for malignancies with low-level Her2/neu expression. Experimental Design: Using fluorescence-activated cell sorting and immunohistochemistry, Her2/neu expression was determined on cell lines derived from Ewing's family tumors (EFT) and neuroblastoma. Sensitivity to trastuzumab treatment was investigated using an in vitro proliferation assay. Cytotoxicity against EFTcell lines was done with either freshly isolated or ex vivo activated and expanded Tcells (cytokine-induced killer cells, CIK cells), with or without addition of a CD3xHer2/neu bispecific antibody. The effects of either trastuzumab, CIK cells alone, or CD3xHer2/neu bispecific antibody redirected CIK cells was determined using a SCID/hu model of EFTs and serial, noninvasive bioluminescent imaging. Results: EFTcell lines express 5-to 10-fold lower levels of her2/neu than either breast (BT-474) or ovarian (SK-OV-3) cell lines.Treatment of EFTcell lines with trastuzumab did not induce growth inhibition either in vitro or in vivo. In contrast, Her2/neu could be used to redirect CIK cell to mediate cytotoxicity against EFTs both in vitro and in vivo (using two different treatment schemas). Conclusions: CD3xHer2/neu bispecific antibody and CIK cells may be a suitable approach to treat malignancies with low-level Her2/neu expression not responsive to trastuzumab.

No abstract

No abstract