Understanding Kras Mutation Heterogeneity in PDAC

Project Summary Pancreatic ductal adenocarcinoma (PDAC) is the most prevalent neoplastic disease of the pancreas, and it is expected to become the second leading cause of cancer related death over the next decade. PDAC has an abysmal prognosis, with only 10% of patients surviving more than 5 years from diagnosis. Interestingly, over 90% of PDACs harbor activating mutations in the KRAS oncogene and the most common KRAS mutations seen in PDAC are G12D, G12V, or G12R. G12D and G12V mutations are commonly found in lung and colon cancers, however G12R mutations are largely restricted to PDAC. 15-20% of PDACs carry G12R mutations, but the majority of preclinical animal models focus on the KrasG12D mutation, which reflects less than half of the KRAS mutations seen in human PDAC. The preliminary data shown in this work and the overall proposal aim to determine if KrasG12R may be functionally distinct from other KRAS driver mutations and how this affects disease initiation and progression. As previously described by us, unlike KrasG12D, KrasG12R mutations do not drive progression to pre-neoplastic PanIN lesions from acinar cells, instead they remain stalled during acinar-to-ductal metaplasia (ADM) and addition of a mutant p53 allele to does not accelerate disease formation in mice. However, we have found that under two specific contexts; KrasG12R / p53MUT ductal- derived organoids transplanted into mice and mice with a p53 mutant allele and loss of the other p53 allele oncogenic transformation happens and results in PDAC formation. We and others have also described decreased PI3K/AKT signaling, in KrasG12R when compared to KrasG12D.This proposed work will test the hypothesis that cell lineage and/or cooperating genetic events in the PI3K pathway impact the oncogenic potential of KrasG12R mutations in pancreas cancer. My proposal represents a significant contribution to understanding the molecular underpinnings of disease initiation and progression of KrasG12R. In the proposed studies we aim to determine if how cell-of-origin impacts disease initiation and progression and how the immediate and sustained molecular events following KrasG12R activation affects initiation and progression. We also aim to elucidate the role of PI3K mutations affect disease initiation and progression in both in vitro and in vivo. To address these questions, we will use lineage tracing mouse models that conditionally mark cells and induce mutant KrasG12R and p53 mutations in the pancreas. In addition, we will use CRISPR-Cas9 genome editing technologies to make complementary organoid and in vivo models of PIK3CA mutations and PTEN deletions that will help elucidate the role of PI3K in KrasG12R PDACs. We plan to use different histological and molecular techniques to dissect the molecular underpinnings of KrasG12R driven PDAC. We anticipate that a better understanding of KrasG12R and related cellular and molecular processes will further elaborate on the KRAS heterogeneity found in PDAC, as well as provide avenues for the development of targeted therapeutics in patient populations with varying KRAS mutations.