ABSTRACT Non-small cell lung cancer (NSCLC) is a highly aggressive disease typically diagnosed at locally advanced or metastatic stage, with dismal prognosis associated with high rates of treatment resistance and disease recurrence. Clinical management of NSCLC varies according to the stage. High-dose stereotactic body radiation therapy (SBRT) is the standard of care for localized non-resectable NSCLC. However, as discovered more than six decades ago, tumor hypoxia is a significant barrier to effective radiation therapy. In the last decade, first line NSCLC treatment has been substantially reinforced with the introduction of immunotherapy targeting immune checkpoints such as programmed cell death 1 (PD-1), yet long-term disease control occurs in less than 25% of NSCLC patients. Therefore, understanding the mechanisms of the treatment resistance is essential to address the dire need of introducing novel synergistic therapies to elicit enhanced treatment response in hypoxic NSCLC tumors. Tumor hypoxia has been associated with anti-cancer treatment resistance for decades, yet its role in clinical management of NSCLC remains largely unexplored. The basis of tumor hypoxia has traditionally been attributed to the oxygen supply deficit as malformed tumor vasculature fails to meet the high demand of the rapidly proliferating tumor mass. However, our preliminary analysis of NSCLC patient datasets in the Cancer Genome Atlas (TCGA) PanCancer dataset revealed a significant correlation between high-level expression of nuclear genes encoding mitochondrial subunits essential for oxidative phosphorylation (OXPHOS), and high- level expression of hypoxia-regulated genes (Buffa hypoxia score). Furthermore, we have observed a direct positive correlation between high frequency of copy number amplification (CNA) of several essential OXPHOS genes, and hypoxia levels in NSCLC patient samples. Because mitochondrial function consumes up to 90% of available cellular oxygen, its activity may be indirectly regulating oxygen availability in the tumor microenvironment by rapidly consuming oxygen upon its delivery to the tumor. Mechanistically, this leads to the hypothesis that OXPHOS gene amplification drives mitochondrial function which may, in turn, promote tumor hypoxia and treatment resistance in NSCLC. The proposed R03 validation study therefore aims to identify the role of high frequency of OXPHOS gene CNA in driving tumor hypoxia and treatment resistance of NSCLC tumors. Upon completion, this study will contribute to current understanding of mechanisms of refractory disease in NSCLC patients and may provide novel markers of treatment outcome.