The overall objectives of this renewal are to use the gene coding for the polyamine catabolic enzyme, spermidine/spermine Nl-acetyltransferase (SSAT), as a model to define additional polyamine responsive genes that play a role in determining drug response. We have identified the cis-element and trans-acting factors that control the antitumor polyamine analogue induction of SSAT. The transcription factor primarily responsible for the analogue inducible expression of SSAT is polyamine-modulated factor-1 (PMF-1). PMF-1 expression is modulated both by the natural polyamines and antitumor polyamine analogues. Since the induction of SSAT activity has been demonstrated to be associated with some, but not all, of the cytotoxic effects of the antitumor polyamine analogues, we will investigate what other genes are regulated by PMF-1 and determine their role in the response to drug exposure.
The specific aims are designed to test the hypothesis that PMF-1 regulated genes play a role in determining the response of tumor cells to the polyamine analogues. By understanding what genes and pathways are regulated by PMF-1 it will be possible to determine more precisely the mechanisms by which the antitumor polyamine analogues kill cells and improve upon the selective nature of their cytotoxic activity. Therefore we will: 1) examine the association between the expression of the SSAT transcription factor PMF-1 and tumor cell response to the polyamine analogues; 2) investigate the molecular mechanisms that regulate the expression of PMF-I. By determining the molecular mechanisms underlying the analogue inducible expression of PMF-1, including the cis- and trans-acting factors responsible for its transcriptional regulation, it should be possible to improve the specific targeting of tumor cells; 3) identify and characterize polyamine responsive genes. It is likely that PMF-1 regulates genes in addition to SSAT and it is possible that these genes play a significant role in determining drug sensitivity and specificity. Using a somatic cell knockout of PMF-1 in combination with microarray analysis of gene expression, it will be possible to identify polyamine analogue-inducible genes and determine if they play a direct role in drug response. Overall, the results of these studies will provide a better understanding of how the polyamine analogues function, what genes and pathways are affected by the analogues, and provide insight as how to target them for therapeutic advantage.
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