Each year, lung cancer kills more than 150,000 Americans. Despite this statistic, the 5-year survival for lung cancer has not significantly improved in the past 30 years. The poor clinical prognosis for NSCLC is linked directly to late-stage diagnosis and high frequency of cancer metastasis. Of all newly diagnosed lung cancers, greater than eighty-five percent of these malignancies are non-small cell lung cancer (NSCLC), with patients presenting with disseminated disease. Therefore, a better understanding of the cellular processes that govern NSCLC metastasis is needed for therapeutic intervention. Sirtuin 6 (SIRT6), a member of the Sirtuin family of histone deacetylases, acts to regulate inflammation, ageing and cancer processes. Although SIRT6 is known to regulate metabolic pathways in cancer, how the culmination of these pathways impact tumor growth and metastasis is poorly understood. In this proposal, we provide evidence that expression of SIRT6 is lost in lung adenocarcinomas and correlates with reduced overall patient survival. Using a conditional mouse model, we identified a group of metabolic genes that are co-regulated by SIRT6 and the transcription factor NF-?B. Interestingly, these gene products generate building blocks required for the synthesis of the nutrient sensor, UDP-N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc is the donor sugar nucleotide used to promote O- GlcNAc transferase (OGT) activity; a pathway implicated in cancer metabolism and metastasis. Since SIRT6 represses NF-?B transcription, we postulate that the loss of SIRT6 in NSCLC sets up a positive feedback loop by which NF-?B drives metabolic reprogramming. Moreover, we find that OGT is required for the proteolytic cleavage and inactivation of chromatin-associated SIRT6. Our overall hypothesis is that SIRT6 functions as a tumor suppressor to inhibit UDP-GlcNAc synthesis and that misregulation of this nutrient sensor stimulates OGT to inactivate SIRT6. To address this hypothesis two Specific Aims will be addressed.
Aim 1 will determine whether the loss of SIRT6 promotes NF-?B B-dependent metabolic reprogramming and will identify critical enzymes that are essential for malignant characteristics.
Aim 2 will elucidate the significance of N-terminal cleaved SIRT6 on NSCLC development and metastasis. Since clinically approved small molecule inhibitors are available that would block the synthesis of UDP-GlcNAc this application provides novel insight into how combinations of these inhibitors could be repurposed and used for the treatment of NSCLC.
Despite being the number one cause of cancer death in the US, overall survival rates for lung cancer have not improved over the past 30 years. Although there are many contributing factors, perhaps the best known reasons are due to late-stage diagnosis and high propensity for metastasis to liver and bone. Currently, elevated glucose uptake is clinically one of the best tumor detection methods. Fluorodeoxyglucose positron emission tomography (FDG-PET) utilizes this heightened glucose uptake to visualize the location of tumors within the body. In the proposal we are studying a protein, call SIRT6, which functions to inhibit pathways responsible for glucose uptake and utilization. We have found that SIRT6 functions to block the production of a specialized sugar metabolite called uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) that is known to be linked with cancer development and metastasis. Importantly, we find that once lung cancer cells misregulate the synthesis of UDP-GlcNAc, that this process can disarm SIRT6 activity and function. Since clinically approved small molecule inhibitors are available that would block the synthesis of UDP-GlcNAc this application provides novel insight into how combinations of these inhibitors could be repurposed and used for the treatment of lung cancer.
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| Liu, Yuan; Amin, Elianna B; Mayo, Marty W et al. (2016) CK2?' Drives Lung Cancer Metastasis by Targeting BRMS1 Nuclear Export and Degradation. Cancer Res 76:2675-86 |
