Metabolic Regulation of Tumor Progression, Metastasis and Chemoresistance by SIRT5/ELK3 signaling in Pancreatic Cancer

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Pancreatic ductal adenocarcinomas (PDAC) are among the most lethal cancers because of their extensive invasion into surrounding tissues and metastasis to distant organs, even during early stages of tumor progression. The poor prognosis for this malignancy also reflects a generally poor response to current therapies. Thus, understanding the biology of these tumors and the mechanisms that promote their invasion and metastasis will provide a basis for developing new methods for diagnosis and treatment. Tumor cells display metabolic alterations that result in enhanced tumor growth or metastasis. Specifically, metabolic reprogramming promotes tumor cell survival under harsh conditions during transit to distant sites and induces proliferation once the tumor cells establish metastatic loci. Aberrant glutamine metabolism is associated with tumor growth in Kras-driven pancreatic cancer. Likewise, our preliminary data demonstrate increased dependence of metastatic lesions on glutamine metabolism. Additionally, we demonstrate that glutamine metabolism regulates responsiveness against gemcitabine by regulating flux through the pyrimidine biosynthesis pathway. We identify SIRT5 as a key negative regulator of glutamine metabolism that diminishes glutamine uptake and dependence in pancreatic cancer cells. SIRT5 diminishes tumor growth and metastasis in orthotopic models. We also observe that SIRT5 negatively regulates the expression of Elk-3, which promotes glutamine metabolism, pancreatic cancer cell survival, and invasiveness. Of particular significance to the proposal, ELK3 is significantly overexpressed by advanced primary and metastatic pancreatic tumor lesions, and hence ELK3- induced metabolic reprogramming is expected to be a target for suppressing pancreatic tumor progression and metastasis. Our long-term goal is to determine the molecular basis of SIRT5/ELK3-mediated metabolic alterations that facilitate progression and metastasis in pancreatic cancer. Here, we hypothesize that SIRT5/ELK3- mediated regulation of glutamine metabolism contributes to tumor progression, metastasis, and chemoresistance in PDAC. Furthermore, we hypothesize that targeting glutamine metabolism can provide a therapeutic strategy to combat tumor progression, metastasis, and chemoresistance in PDAC. Here, we propose to characterize the metabolic phenotype in SIRT5-deficient pancreatic tumor models (Aim 1) and investigate if Elk3-mediated transcriptional and metabolic reprogramming contributes to SIRT5-mediated metabolic phenotype (Aim 2). Furthermore, we propose to elucidate the role of ELK3 in regulating tumor progression, metastasis, and gemcitabine resistance in PDAC (Aim 3). These studies will elucidate the metabolic aspects of SIRT5/ELK3-mediated tumor progression and metastasis and are strongly expected to uncover additional therapeutic strategies for the treatment of pancreatic cancer.