Pancreatic cancer is a deadly disease that is virtually never cured, therefore our long-term goal is to develop therapeutic regimens for pancreatic cancer patients that sensitize these chemo-resistant tumors to therapy and achieve prolonged patient response. This proposal will investigate to what extent impairing the ability of the pancreatic cancer cells to respond to DNA damage following therapy will result in an increase in response to treatment with DNA damaging agents. To increase the efficacy of chemotherapy in pancreatic cancer cells, we plan to inhibit a key protein in the DNA base excision repair (BER) pathway. The BER pathway including apurinic/apyrimidinic endonuclease/redox factor (Ape1/Ref-1 or Ape1) plays a major role in the repair of damage caused by chemotherapeutic agents. In addition to DNA repair activity, Ape1 also interacts with a number of transcription factors (Hif1-a, p53, AP1, NF?B, etc) to facilitate their DNA binding. Gemcitabine, a DNA chain terminator, is the foremost chemotherapeutic agent currently used to treat pancreatic cancer. Studies demonstrating a role for the 3' to 5' exonuclease activity of Ape1 in the excision of deoxyribonucleoside analogs from DNA provide rationale for combining Ape1 DNA repair inhibitors with gemcitabine treatment. In addition, a reduced level of Ape1 protein sensitized pancreatic cancer cells to gemcitabine. Furthermore, NF?B is known to be under redox control by Ape1, and Nf?B activity is a determinant of pancreatic cancer cells' response to gemcitabine. We have the ability to examine the endonuclease and the redox functions of Ape1 independently by using small molecules that block both of Ape1's functions. Therefore, our short term goal is to establish Ape1 as a target to sensitize pancreatic tumors to chemotherapy. Dismal response rates in pancreatic cancer necessitate better and novel therapies, therefore we propose the use of temozolomide (TMZ) in combination with Ape1 redox/DNA repair inhibitors. TMZ is an alkylating agent which creates DNA lesions that are repaired by the BER pathway. We have preliminary data demonstrating a dramatic enhancement of TMZ-induced cytotoxicity in combination with small molecule Ape1 inhibitor, methoxyamine (MX) in pancreatic cancer cell lines. TMZ is, therefore, an excellent candidate for combination therapy in pancreatic cancer involving Ape1 inhibitors in addition to gemcitabine. The overall hypothesis of the proposed work is that treatment of pancreatic cancer with gemcitabine and TMZ can be improved by blocking the activity of Ape1 and the repair of DNA lesions. In addition to the clinical application of enhanced sensitivity to chemotherapy (gemcitabine or TMZ) in the presence of Ape1 DNA repair or redox inhibitors, we will also gain a more thorough understanding of the mechanism of pancreatic cells' response to gemcitabine or TMZ and the role that Ape1 plays in that response. Pancreatic cancer is a deadly disease that is virtually never cured and known to be resistant to most chemotherapy regimens. We want to sensitize these chemo-resistant tumors to therapy and achieve prolonged patient response by inhibiting a protein involved in DNA repair and redox signaling, Ape1. This proposal will investigate to what extent impairing the ability of the pancreatic cancer cells to respond to DNA damage following chemotherapy will result in an increase in response to treatment with DNA damaging agents, gemcitabine and temozolomide. ? ? ?
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