Defects in death receptor-mediated apoptosis have been linked to cancer and autoimmune disease in humans.The in vivo role of caspase 8, a component of this pathway, has eluded analysis in postnatal tissues because of the lack of an appropriate animal model. Targeted disruption of caspase 8 is lethal in utero. We generated mice with a targeted caspase 8 mutation that is restricted to the T-cell lineage. Despite normal thymocyte development in the absence of caspase 8, we observed a marked decrease in the number of peripheral T-cells and impaired T-cell response ex vivo to activation stimuli. caspase 8 ablation protected thymocytes and activated T-cells from CD95 ligand but not anti-CD3-induced apoptosis, or apoptosis activated by agents that are known to act through the mitochondria. caspase 8 mutant mice were unable to mount an immune response to viral infection, indicating that caspase 8 deletion in T-cells leads to immunodeficiency. These findings identify an essential, cell-stage-specific role for caspase 8 in T-cell homeostasis and T-cell-mediated immunity. This is consistent with the recent identification of caspase 8 mutations in human immunodeficiency.

Purpose: This study aims to identify a novel therapeutic agent for head and neck cancer and to evaluate its antitumor efficacy. Experimental Design: A cell-based and phenotype-driven high-throughput screening of f2,400 biologically active or clinically used compounds was done using a tetrazolium-based assay on FaDu (hypopharyngeal squamous cancer) and NIH 3T3 (untransformed mouse embryonic fibroblast) cells, with secondary screening done on C666-1 (nasopharyngeal cancer) and GM05757 (primary normal human fibroblast) lines. The ''hit'' compound was assayed for efficacy in combination with standard therapeutics on a panel of human cancer cell lines. Furthermore, its mode of action (using transmission electron microscopy and flow cytometry) and its in vivo efficacy (using xenograft models) were evaluated. Results: Benzethonium chloride was identified as a novel cancer-specific compound. For benzethonium (48-hour incubation), the dose required to reduce cell viability by 50% was 3

Purpose: A wide variety of tumors depend on the dysregulation of Bcl-2 family proteins for survival. The resulting apoptotic block can often provide a mechanism for resistance to anticancer treatments, such as chemotherapy and radiation.This current study evaluates the efficacy of combining systemically delivered Bcl-2 phosphorothioate antisense (Bcl-2 ASO) and radiation for nasopharyngeal cancer therapy. Results: Antisense uptake was unaffected by 0, 3, or 6 Gy radiation. Radiation decreased the fraction of viable C666-1cells to 60%, with a further decrease to 40% in combination with Bcl-2 ASO. Despite a modest in vitro effect, Bcl-2 ASO alone caused the regression of established xenograft tumors in mice, extending survival by 15 days in a C666-1and by 6 days in a C15 model. The survival times for mice treated with both Bcl-2 ASO and radiation increased by 52 days in C666-1and by 20 days in C15 tumors. This combination resulted in a more-than-additive effect in C666-1tumors. Less impressive gains observed in C15 tumors might be attributable to higher expression of antiapoptotic Bcl-2 family proteins and limited drug distribution in the tumor. Retreatment of C666-1 tumors with the Bcl-2 ASO-radiation combination, however, was effective, resulting in mice surviving for >80 days relative to untreated controls. Conclusions:Our results show that the Bcl-2 ASO and radiation combination is a highly potent therapy for nasopharyngeal cancer. Further examination of combination therapy with radiation and other Bcl-2 family^targeted anticancer agents in both preclinical and clinical settings is definitely warranted.