We are conducting phase I/II clinical trials using adenoviral vectors expressing tumor necrosis factor (TNF) to treat patients with pancreatic cancer. TNF expressed from adenoviral vectors can enhance tumor cell killing but can also leak into the systemic circulation causing serious toxicities. To overcome this problem, we have developed novel chimeric forms of TNF with enhanced antitumor activity and greatly reduced systemic toxicity. Our chimeric TNF molecules have been designed to minimize the proteolytic release of free soluble TNF from the cell surface thereby restricting the expression of TNF to the membrane of the cell. We have developed an immunocompetent mouse model of pancreatic cancer that simulates the clinical pattern of pancreatic tumor growth, progression, neovascularization and metastasis observed in human tumors. We propose using this model, which recapitulates both locally advanced and metastatic pancreatic cancer, to evaluate the toxicity and efficacy of the chimeric TNF vectors when used alone and in combination with the chemotherapeutic agent gemcitabine. Our hypothesis is that expression of membrane-bound forms of TNF will minimize systemic toxicity, enhance tumor specific immunity and improve therapeutic efficacy compared to expression of wild-type TNF and when used alone and in combination with gemcitabine.
The specific aims of the study are: 1) Determine the expression of wild-type and membrane bound forms of TNF in a panel of established mouse and human pancreatic tumors cell lines. To do this, each tumor cell line will be characterized with respect to expression of TNF on the cell surface by flow cytometry, release of TNF into the culture media by immunoassay and TNF tumoricidal activity by bioassay; and 2) Determine the maximum tolerated dose of adenoviral vectors expressing wild-type and membrane bound forms of TNF in an orthotopic, immunocompetent mouse model of metastatic pancreatic cancer and to determine the impact of the expression of various forms of TNF on tumor growth, tumor vascularity, tumor specific immunity and metastasis when used alone or in combination with gemcitabine in the orthotopic, immunocompetent mouse model. Tumor necrosis factor (TNF) is a protein made by the body that can kill tumor cells directly and also enhance the immunity against the tumor cells. We have developed adenoviral vectors that can be used to infect and produce high levels of TNF in the tumor cells. To improve therapeutic efficacy, we have developed a stabilized form of TNF that cannot be released from the surface of the tumor cells. ? ? ?