Pancreatic ductal adenocarcinoma (PDAC) is a disease of near uniform mortality, and with few tangible therapeutic modalities. Failure of traditional therapy is due to our limited understanding of how the tumor microenvironment (TME) can facilitate the rapid progression or recurrence of PDAC. Altered cellular metabolism is a hallmark of cancer cells, and much of the published literature has focused on neoplastic cell autonomous processes for these adaptations. Although cancer-associated fibroblasts (CAFs), a major cellular component of TME, have been associated with tumor growth and metastasis through intercellular communications with cancer cells; little is known about their role in inducing metabolic reprogramming in cancer cells. Studies have shown that extracellular vesicles known as exosomes have emerged as a vital communication mechanism between different cell types in the TME. Exosomes carry information from one cell to another and reprogram the recipient cells, and recent findings report that exosomes harbor the potential to regulate proliferation in recipient cells. Most of the current studies are focused on cancer cell secreted exosomes; and little is known about CAF-derived exosomes (CDEs) and their metabolic influence on cancer cells. Although it has been shown that CAFs can metabolically reprogram cancer cells, the contribution of CDEs in this phenomenon, if any, has not been elucidated. We propose a novel regulation of cancer cell metabolism in PDACs mediated by CDEs. First, we hypothesize that CDEs reprogram cancer cell metabolism through miRNA based disabling of mitochondrial oxidative metabolism. Second, CDEs provide de novo ?off the shelf? metabolites through exosomal cargo to PDAC cells. We will test these hypotheses in the proposed aims. First, to understand the underlying metabolic alterations induced by CDEs in cancer cells, we will perform 13C GC-MS based isotope tracer analysis. To unravel the mechanism behind metabolic alterations in cancer cells by CDEs, we will estimate the changes in metabolic gene expression in cancer cells with CDEs. Second, we will characterize the metabolite cargo in CDEs using intra-exosomal metabolomics. We will dissect the mechanisms by which CDEs (either indirectly through miRNAs, or directly through nutrient cargo) regulate cancer cell metabolism. Further, we will investigate whether CDEs regulate BCAA metabolism in PDAC cells. Third, we will establish the efficacy of CDE-mediated metabolic enrichment of cancer cells in vitro and in mouse pancreatic tumors. We will examine the intra-exosomal metabolites contribution in enriching PDAC cells? proliferation. Using labeled exosomes in two distinct systems: the first, using orthotopic patient-derived low-passage cell lines (PDCLs) and the second, using syngeneic allografts using Kras; p53 (?KPC?) murine cells generated in a B6 background we will determine if the labeled metabolites from CDEs are being incorporated into the tumor cells and stimulate tumor growth. In summary, our proposed study can lead to novel therapeutics targeting communication between cancer cells and their microenvironment.
This project is highly significant and directly relevant to public health since it focuses on developing new methods for targeting pancreatic cancer growth and metastasis by targeting coupling between tumor microenvironment and pancreatic cancer cells. This proposal's overarching objective is to uncover a novel role of exosomes within the tumor microenvironment in regulating the metabolic adaptation observed in pancreatic cancer cells, and uncovers the underlying mechanism of this regulation. Disruption of this exosomes-induced metabolic adaptation in cancer cells might provide a novel therapeutic avenue for exploitation.
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|Salimian Rizi, Bahar; Achreja, Abhinav; Nagrath, Deepak (2017) Nitric Oxide: The Forgotten Child of Tumor Metabolism. Trends Cancer 3:659-672|