H3K9 Methylation and Pancreatic Cancer Chemoresistance

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DESCRIPTION (provided by applicant): Pancreatic cancer is a death sentence for patients diagnosed with this disease, as there are few effective treatments. Gemcitabine is currently the standard therapy for human pancreatic cancer patients. However, gemcitabine only increases survival rate of human pancreatic cancer patients with advanced disease by a medium time of 5 weeks since human pancreatic cancer cells are often resistant to gemcitabine. Therefore, development of novel agent that can overcome pancreatic cancer resistance to gemcitabine is in urgent need. We have recently discovered that a natural compound (verticillin A) purified from pathogen-infected wild mushrooms can effectively overcome resistance of human cancers to therapeutic agents both in vitro and in vivo. We have now identified the molecular target of verticillin A: Verticillin A is a specific inhibitor of histone methyltransferases (HMTases) SUV39H1, SUV39H2, G9a and GLP, all of which catalyze methylation of lysine 9 of histone H3 (H3K9). Verticillin A inhibits these HMTases to de-methylate H3K9me2 and H3K9me3, resulting in transcriptional activation of epigenetically silenced apoptosis-regulatory genes and sensitization of human cancer cells to apoptosis- inducing therapeutic agents. Importantly, we observed that verticillin A is extremely effective in sensitization of human pancreatic cancer cell to gemcitabine-mediated growth inhibition in vitro. The objective of this project is to elucidate te mechanism of verticillin A action in human pancreatic cancer cells and to determine the efficacy of verticillin A in vivo. Our hypothesis is that verticillin A inhibits H3K9 methylation to reactivte transcription of epigenetically silenced apoptosis regulatory genes to sensitize human pancreatic cancer cell to gemcitabine-induced apoptosis. To test this hypothesis, we will pursue 2 specific aims: 1) test the hypothesis that verticillin A overcomes human pancreatic cancer resistance to gemcitabine through inhibition of H3K9 methylation to activate transcription of apoptosis regulatory genes; and 2) determine the efficacy of verticillin A in overcoming pancreatic cancer resistance to standard chemotherapeutics in vivo. Successful completion of the proposed studies has the potential to develop verticlillin A as an adjunct agent to overcome pancreatic cancer resistance to gemcitabine in human cancer therapy.