Lung cancer is the leading cause of cancer deaths in the United States. Although advances have been made in treatments for lung cancer, only 16% of patients diagnosed with lung cancer survive the disease beyond 5 years. Therefore, there is a dire need to develop new, more-effective treatments for lung cancer. Lung squamous cell carcinoma (LSCC) is a major and aggressive subtype of lung cancer for which there are currently no targeted therapies. The major risk factor for development of LSCC is tobacco smoking. Military personnel and Veterans are more likely to use tobacco and to develop lung cancer than the civilian population. Within LSCC tumors are a population of cells termed cancer stem cells (CSCs) that are highly aggressive and are capable of fueling the growth and metastasis of tumors. CSCs are also notoriously resistant to current chemotherapeutic treatments. These findings have led to the hypothesis that LSCC CSCs must be eliminated to obtain effective treatment and lasting remission of patients with LSCC. We have identified a protein, Protein Kinase C iota (PKC iota) that, when overactive, can cause LSCC CSCs to grow. Specifically, we have shown that PKC iota is required for the growth of LSCC CSCs by regulating the Hedgehog (Hh) pathway, an important pathway for the growth of CSCs. We previously discovered that the compound Auranofin (ANF), which is approved by the Food and Drug Administration (FDA) for the treatment of rheumatoid arthritis, can inhibit PKC iota activity. Based on these data, we hypothesize that combined therapy with ANF and an Hh pathway inhibitor will more effectively eliminate CSCs and thereby block the growth of LSCC tumors with overactive PKC iota activity. Our studies address several Lung Cancer Research Program Areas of Emphasis, including: (1) increasing our understanding of important factors involved in lung cancer progression; (2) identifying a new therapy for LSCC; and (3) developing biomarkers to identify patient populations that that may respond to our proposed therapeutic approach and to monitor patient response. Completion of these studies will help in the design of a novel strategy to eliminate LSCC CSCs that may provide effective, long-term treatment for LSCC patients. Both ANF and Hh inhibitors are FDA-approved; therefore, clinical testing in LSCC patients can begin immediately after we demonstrate that this combination of drugs is effective based on the laboratory studies that are outlined in this proposal. LSCC accounts for ~30% of all lung cancer cases (~67,500 per year in the United States), of which ~90% show overactive PKC iota activity; therefore, if our combination strategy is proven effective, this new therapy could positively affect the lives of a large percentage of patients diagnosed with lung cancer every year.