Validation of a Mouse Model of Pancreatic Carcinogenesis

Overview

The primary aim of this study is to determine if mutations of BRCA1 and BRCA2 result in different precancerous pathways to pancreatic ductal adenocarcinoma (PDAC), as suggested in our validated mouse model. Genomic DNA will be isolated on normal tissue obtained from patients who underwent pancreatic resection for PDAC, intraductal papillary mucinous neoplasm (IPMN) or mucinous cystic neoplasm (MCN). Tissue will be examined for the three most common founder mutations in Ashkenazi Jews. In the cases in which BRCA1 or BRCA2 mutations are found, heterozygote normal and abnormal tissue will be examined to look for mutations in the other BRCA1 or BRCA2 allele. The interaction between other cancer causing genes with BRCA1/2 will also be evaluated by comparing the sequences of the other genes in pre-cancerous lesions. We hypothesize that BRCA1- and BRCA2-mediated pancreatic ductal adenocarcinoma progresses through the PanIN route, as seen in both BRCA1 and BRCA2 murine models of pancreatic cancer. We further hypothesize that BRCA1 mutations may enable an additional pre- neoplastic pathway through MCN, and that IPMN may embody yet another pre- neoplastic pathway.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of death from malignancy in the United States. Several gene mutations and cancer syndromes have been identified that are found in greater frequency in individuals with PDAC, including the breast ovary cancer syndrome (BRCA1 and BRCA2 mutations). We have recently generated mouse models of pancreatic cancer in which we found that deletions of either BRCA1 or BRCA2 cooperate with K-ras activation and p53 mutations to increase the rate of tumorigenesis via accelerated progression of Pancreatic Intraepithelial Neoplasia (PanIN). However, only BRCA1 deletions were associated with the development of concomitant Mucinous Cystic Neoplasms (MCNs), suggesting potentially distinct pathways for BRCA1- and BRCA2-mediated tumorigenesis in the pancreas. Our primary aim is to determine if germline mutations of BRCA1 and BRCA2 result in different pre-neoplastic pathways to pancreatic cancer, as in our murine model. Genomic DNA will be isolated on normal tissue obtained from patients who underwent pancreatic resection for pancreatic cancer, IPMN or MCN. Tissue will be genotyped for the three most common founder mutations in Ashkenazi Jews. In the cases in which BRCA1 or BRCA2 mutations are found, heterozygote normal and abnormal tissue will be microdissected to look for loss of heterozygosity at the BRCA1 or BRCA2 allele. Our secondary aim is to evaluate the interaction of p53 and Kras with BRCA1 and BRCA2 by sequencing p53 and Kras in PanIN as compared to IPMN and MCN lesions.