Dissecting the role of ATM in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and one of the deadliest solid tumors. Activity of the ataxia-telangiectasia-mutated (ATM) kinase is crucial for DNA damage responses induced by double-strand breaks. Deep-sequencing studies identified inactivating ATM somatic mutations in sporadic pancreatic tumors presenting a very aggressive form of the disease. Also, ATM germline mutations were found to correlate with increased susceptibility to Familial Pancreatic Cancer. Our laboratory is currently exploring how ATM deficiency affects pancreatic cancer progression. To this effect, we generated mice carrying oncogenic Kras expression and ATM deletion in the pancreas. We found that ATM deficiency accelerates metastatic PDAC formation in a dosage-dependent manner. To further understand why tumors lacking ATM expression are highly aggressive, we established primary cultures from individual mouse pancreatic tumors and their corresponding liver metastasis. Results of chromosomal analysis uncovered increased genomic instability in the ATM-deficient tumor cell lines in comparison to ATM-proficient tumor cells. My follow-up studies will use RNA sequencing to compare gene expression profiles in the former cell lines to identify pathways that increase metastatic potential in ATM-deficient PDAC. We also found that ATM-deficient tumor cells are radiosensitive whereas ATM-proficient tumor cells are not, and I will use combinations of DNA-damage chemotherapeutic drugs to test synthetic lethality and identifying compounds that effectively eliminate pancreatic tumor cells lacking ATM. We also identified increased expression of the cancer stem cell (CSC) marker Prominin 1 in ATM-deficient pancreatic tumor cells. Thus, I will use established protocols to isolate CSCs from ATM-proficient and ATM-deficient PDAC cells to compare these cell populations using various approaches. Finally, I will isolate acinar cells from our ATM-mouse models and cultured them in 3D collagen gels to investigate why ATM deficiency accelerates early Kras-induced neoplastic transformation.