Abstract 48,960 new cases of pancreatic cancer were predicted for 2015 and despite extensive treatment options, the 5 year relative survival rate has consistently remained below 8% for the past 40 years. Current treatments are non- targeted agents with inherent side effects and only prolong survival on the order of months. Kras is mutated in over 90% of pancreatic adenocarcinoma (PDAC), the most common type of pancreatic cancer. Under normal conditions, Kras is a tightly regulated signaling protein that can toggle between active and inactive states to control cell proliferation. Mutated Kras (G12D) predominantly remains active, thus, constitutively promoting proliferation and tumorigenesis. Studies that target downstream pathways of Kras, Raf/ERK and PI3K/AKT, have had some preclinical success but minimal clinical impact on pancreatic cancer. Therefore, it remains possible that other undiscovered protein-protein interactions exist, including transient ones. This study aims to identify such interactions via cutting edge proteomics technique, BioID (a promiscuous biotin ligase). Firstly, BioID fusions to wild type and mutant Kras will be expressed in mouse tumor cells and human pancreas cell lines to differentially label local proteins, and thus identify context specific interactors of Kras. The relative amounts of proteins will be measured using mass spectrometry and western blot analysis. Preliminary data in murine cells reveal that Rab42 is a major Kras effector. Secondly, depletion experiments of this protein of interest will be performed to study the role of Rab42 in proliferation, transformative potential, EGF dependency, tumorigenesis, and invasive potential in vitro. The role of Rab42 in tumor initiation and engraftment will be determined in vivo with orthotopically grafted organoid (OGO) mouse model. This proposed study will identify mutant specific Kras effectors and hopefully lead future studies to novel therapeutic targets for mutant Kras- driven PDAC. Knowledge that comes out of this study may also shed light on other Kras mutant cancers such as lung and colon adenocarcinoma.