TARGETING DEATH RECEPTOR-MEDIATED APOPTOSIS FOR HEAD AND NECK CANCER

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The long-term goal of our research is to identify and develop novel and efficacious therapeutic regimens for the treatment of human cancer, particularly head and neck cancer (HNC). The current application aims specifically at targeting death receptor-mediated apoptotic pathways for the treatment of HNC, particularly metastatic HNC, through evaluating the potential of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or perifosine and TRAIL in combination in the treatment of metastatic HNC. Our gene array and Western blotting data indicate that highly metastatic HNC cell lines express increased levels of death receptor 5 (DR5), FADD, caspase-8 and caspase-9 and low levels of c-FLIP(L) although they exhibit undetectable levels of TRAIL and high levels of c-FLIP(S). Importantly these cell lines are highly sensitive to exogenous TRAIL treatment. Perifosine, the first oral alkylphospholipid with Akt-inhibitory activity in clinical trials, further upregulates the expression of DR5, reduces c-FLIP levels and very effectively induces apoptosis in these metastatic HNC cell lines. Based on these findings, we hypothesize that highly metastatic HNC cells retain high potential to undergo DR5-mediated apoptosis, albeit with dysregulated apoptotic signaling. Thus, agents including TRAIL and perifosine that activate the DR5-mediated apoptoticpathway may be effective in treatment of metastatic HNC. These hypotheses will be tested by accomplishing the following specific aims: 1) Determine the mechanism(s) by which perifosine and TRAIL cooperatively induce apoptosis of metastatic HNC cells; 2) Determine the efficacy of TRAIL and its combination with perifosine in an in vivo model of HNC metastasis; and 3) Determine differential expression patterns of selected genes (e.g., TRAIL, DR5, c-FLIP, and caspase-8) primarily involved in the extrinsic apoptotic pathway between primary and metastatic human HNC tissues, and evaluate their prognostic values. The accomplishmentof these aims will allow us to assess the efficacy of TRAIL and its combination with perifosine in the treatment of HNC, particularly metastatic HNC, in vitro and in vivo, reveal the underlying mechanisms of perifosine and TRAIL synergism, and demonstrate the role of dysregulation of the extrinsic apoptotic pathway in HNC metastasis and its prognostic value. The results generated from this project can be directly translated to clinical practice for the better treatment of HNC patients.