Project 1 SUMMARY A clearer understanding of how tumor cells survive the stress of platinum agents and evolve into therapy resistant populations is essential to overcome treatment failure and maximize both disease control and survival. Our data demonstrate that HNSCC cell lines with acquired cisplatin resistance reduce glycolytic and mitochondrial energy production while increasing carbon flux into anabolic pathways. This results in an enhanced reductive potential (glutathione, NAD(P)H, FADH2) via both glucose and glutamine catabolism coupled to increased glutathione (GS) peroxidase 2 (GPX2) activity coordinated at a genomic and transcriptional level, partially through the KEAP1-NRF2 pathway. Hyperactivation of GPX2 concomitantly likely inhibits NF-κB activation, decreasing chemokine and prostaglandin production by tumor cells— leading to a suppressive tumor immune microenvironment (TIME) enriched for myeloid derived suppressor cells (MDSCs) and depleted of cytotoxic tumor infiltrating lymphocytes (TILs). It is our central hypothesis that this metabolic adaptation is a permissive and required step for acquisition of cisplatin resistance. We further postulate that this metabolic shift transitions some tumors to an immunologically silent phenotype, which reduces immune surveillance to compound the aggressive behavior and cross-therapy resistance of CDDP-treated tumors We will first define the critical metabolic steps required for generation of an enhanced reductive state that supports cisplatin resistance in Aim 1. We will utilize in vitro and in vivo orthotopic HNSCC models to measure the contribution of glucose and glutamine to GS synthesis in cisplatin resistant tumors and, using chemical inhibition coupled to shRNA blockade of individual transporters and enzymes, identify the critical rate limiting metabolic steps for GS synthesis and cisplatin resistance in HNSCC. In Aim 2 we will determine how GS synthesis and utilization (by GPX2 and non GPX means) are coordinated transcriptionally at least in part through Nrf2 in order to support cisplatin resistance. In Aim 3 we will test the impact of GS metabolism via canonical (e.g. NF-kB) and metabolic paracrine signaling on development of a suppressive TIME. Completion of the proposed experiments will: 1) identify suitable targets for ablation of the enhanced reductive state driving cisplatin resistance in HNSCC and 2) identify metabolic biomarkers which can be coupled to 13C flux imaging-based measurements to generate real-time readout of tumor treatment response, and inform a more personalized approach to targeting metabolism to overcome CDDP resistance. By identifying the critical mechanistic underpinnings of metabolic adaptation, we can generate a paradigm shift in our capability to both rapidly detect acquisition of resistance to genotoxic stress and to overcome it using multiple clinically viable approaches. It will further shed light on how acquisition of cisplatin resistance can impact resp...