The translations! goal of this project is to develop new target-directed drugs for the treatment of colorectal cancer. Colorectal tumors exist in a stressed environment. As they grow, they outstrip new blood vessel formation leading to poor perfusion, nutrient deprivation and hypoxia. Cancer cells adapt to this stress by changes in key cell survival signaling pathways leading to resistance to cell death, increased anaerobic metabolism, new blood vessel formation and increased metastasis. Although the changes give aggressive, resistant tumors they also provide an Achilles heel for selectively attacking the tumor because without the changes the cancer cells will die. The hypothesis upon which our studies are based is that the signaling pathways that regulate the growing tumor's response to inadequate blood perfusion, nutrient deprivation and hypoxia provide novel targets for the development of agents to selectively treat cancer. We will study two pathways and conduct two clinical trials in colorectal cancer of agents developed by us that inhibit the pathways. The first pathway is the thioredoxin-1 (Trx-1) redox signaling pathway and its inhibitor PX-12 that has already shown antitumor activity in patients with colorectal cancer in a Phase I trial. We have show that PX-12 inhibits the hypoxia ? inducible factor-1 and the Sp1 mediated increase in tumor VEGF formation, EGFR and IGF-1R expression and increases the activity of the Nrf2 transcription factor that plays a dual role in regulating polyamine metabolism through the polyamine response element (PRE) and the antioxidant defense through the antioxidant response element (ARE) in cancer cells. The second pathway is the phosphatidylinositol-3- kinase (PI-3-K) stress signaling pathway, the most frequent signaling abnormality in human cancer. PI-3-K is mutated and activated in many colorectal cancers. We have developed PX-866 a potent inhibitor of PI-3-K and identified a potential biomarker for predicting response.
The specific aims are:1) to investigate the mechanisms for the redox regulation of transcription factors by Trx-1 and its reversal by PX-12; 2) to conduct a Phase l/llclinical trial of PX-12 in colorectal cancer with mechanistic molecular marker and imaging; 3) to investigate mechanisms mediating the response to PI-3-K inhibition in colorectal cancer; and 4) to conduct a Phasel/ll clinical trail of PX-866 in colorectal cancer with mechanistic marker and imaging studies. The long-term goal of our work is to conduct translational studies of the mechanisms of stress induced gene expression that will lead to the development of novel agents for colorectal cancer treatment.
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