Cancer immunotherapy (IMT) can produce robust and durable anti-tumor immune responses in some cases. However, many cancers are non-responsive to IMT and combination approaches need to be actively investigated, particularly in lethal tumors such as IMT-insensitive non-small cell lung cancer (NSCLC). Preclinical studies in general have been found to be poor predictors of success for IMT agents and chemoradiotherapy combinations in the clinic, likely due to poorly conceived and executed treatment protocols, dated disease model systems and lack of an existing framework for cross-validation of preclinical results. There is a need to develop a rigorous preclinical testing program for existing IMT agents combined with chemoradiation. NSCLC genetically engineered mouse models (GEMMs) of the major molecular NSCLC subtypes have been created. However, there are no NSCLC GEMMs that to our knowledge has demonstrated “abscopal” responses reliably to IMT, which is one unique strength of this current proposal. Also, a major limitation of existing GEMMs is the relatively small number of different genotypes that can be generated and their lack of quantitative precision. This proposal leverages a new technique, tumor barcoding with barcode deep-sequencing (Tuba-seq) and in vivo Cre-lox and CRISPR/Cre-mediated GEMMs to model oncogenesis and radiation-drug response with unprecedented precision and genomic-comprehensiveness. We are using this R01 mechanism in the present proposal via two Specific Aims stated below to test the following central hypotheses: (i) we hypothesize that treating with both anti-PD-L1 and a novel orally bioavailable ATR inhibitor (ATRi), AZD6738, in combination with chemoradiation will result in an improved and durable anti-tumor immune response in poorly immunogenic NSCLC GEMMs; and, (ii) Tuba-seq we will allow an unprecedented view of the radio-pharmacogenetic landscape of NSCLC responses in vivo. SPECIFIC AIM #1 – Establish a radio-pharmacogenetic map of oncogene-driven non-small cell lung cancer to both chemoradiation and combined chemoradiation/anti-PD-L1 therapy We propose to use novel CRISPR/Cre-mediated GEMMs of NSCLC to test the optimal combinations of chemoradiation with anti-PD-L1 IMT. We will then examine the mechanism of action of chemoradiation with IMT using multiparametric immunologic approaches and an innovative technique enabling lineage tracing and direct quantification of treatment effects on these different genetic backgrounds in vivo. SPECIFIC AIM #2 – Determine tumor cell genotype effects on combination anti-PD-L1 immunotherapy and ATRi with chemoradiotherapy in oncogene- driven non-small cell lung cancer. This Aim leverages our novel CRISPR/Cre-mediated GEMMs of NSCLC to test genotype effects on the combination of anti-PD-L1 and ATRi with chemoradiation. By using all these tools, we will be able to decode the major aspects of the molecular underpinnings of chemoradiation and combination IMT resistance in NSCLC, contribut...