PROJECT 2 SUMMARY After several decades of intensive efforts from academia and industry, targeting KRAS using KRAS-specific inhibitors (KRASi) such as sotorasib and adagrasib has finally become a clinical reality. However, clinical reponses to KRASi vary widely across different cancer types (higher in lung cancer, but much lower in colon and panceraic cancers) and are typically not durable. Importantly, cancers that eventually became resistant to KRASi were found to have acquired secondary mutations that restore KRAS signaling. For these patients, there is still a strong need for therapeutic combinations that can abrogate KRAS signaling pathways such as the RAF-MEK- ERK (MAPK) or PI3K-AKT cascades. To meet these clinical needs, Project 2 of the WU-PDTC aims at testing three novel therapeutic combinations to deepen the therapeutic response of KRASi in different KRAS-mutant cancer PDXs. Because these combinatorial strategies were developed from panceratic cancer models, we will also preform start-of-the-art proteo-transcriptomic analyses to determine the shared and distinct primary and secondary resistance mechanisms of pancreatic, lung and colon cancer PDXs to KRAS and MAPK pathwya inhibtiors. Our project capitalizes on the large repertoire of genetically-defined PDX models from different cancer types, is based on novel exciting biology, supported by state-of-the-art technqiues including innovative 3D- heterotypic culture model, spatio-transcriptomics, snRNAseq, multiplex immunohistochemistry and an outstanding bioinformatic team. We have strong institutional commitment to provide additional fund to ensure this Project is smoothly executed. Our novel therapeutic concepts are based on therapeutic agents that are already in clincial trials. If successful, results from our Project can be immediately translated into biomarker- driven clinical trials under the NCI Experimental Therapeutics Clinical Trials Network, in which WU is an active participating member.