Tumor Necrosis Factor alpha (TNF) is a pleiotropic cytokine that was originally discovered as an agent that caused the destruction of tumors in endotoxin treated mice. It is now known to be involved in inflammation, septic shock, organ rejection, and HIV gene activation. TNF has also been shown to cause the cytolysis of some but not all transformed cells in vitro . The ability of normal cells to resist TNF-mediated cytolysis is dependent on the transcription of """"""""resistance"""""""" genes, as inhibition of transcription leads to cytolysis. To understand the mechanisms of TNF action and resistance we have isolated twenty-two TNF-induced genes from cDNA libraries. Four of the cDNAs are encoded within the mitochondrial genome and seven are novel genes. The remaining genes, whose products were identified by comparison to known DNA sequences, are involved in aspects of inflammation, tissue repair, and metabolism. In this proposal, this collection of TNF-induced genes will be used to characterize and elucidate the mechanisms TNF action and resistance to cytolysis. Experiments are designed to determine the relationship between the induced genes and resistance to TNF. This will be carried out by comparing the expression of the genes in a large panel of cell lines that are either resistant or sensitive to TNF. Constructions that constitutively express putative """"""""resistance"""""""" genes will be used to determine if the induced genes are sufficient to provide resistance in sensitive cells or augment the expression of the other TNF regulated genes. To understand the molecular mechanisms by which TNF-induced genes are regulated, experiments are proposed to identify and characterize the cis-acting regulatory elements and the trans-acting factors that control the response to TNF. These experiments will focus on the manganese superoxide dismutase gene, a TNF-induced gene whose product is associated with resistance to TNF. The study of TNF resistance will help us understand how cells survive exposure to TNF and in the long term may allow the design of new therapies that increase the relative sensitivity of tumor cells to TNF. By understanding how TNF regulates gene expression, a means to control the beneficial and detrimental effects of TNF may be possible.
