In neoplastic diseases, cellular reprogramming for continued proliferation, invasion and metastasis are essential for tumor initation and progression. An increased understanding of oncogene regulation of these processes is essential to successful therapy. Our research has focused on the essential role of altered bioenergetics and biosynthetic metabolism during cell cycle entry and tumor progression regulated by the oncogene c-Myc. We have recently developed a novel approach to trace metabolism of nutrients and their direct contribution to protein modifications and demonstrated regulation of histone acetylation by substrate supply during Myc-dependent cell cycle entry, a previously unappreciated connection between metabolism and post-translational modifications. Increased lipid biosynthesis in Myc-expressing cells may increase protein targeting to lipid rafts and our preliminary studies indicate increased raft-associated Ras protein during Myc- induced cell cycle entry. We also demonstrated increased prostaglandin E2 in media, and that cyclooxygenase inhibitors had selective anti-proliferative effects for Myc-expressing cells. Lastly, our stable isotope studies with a Myc inducible/regressible tumor model show that tumor initiation, progression and regression are associated with distinct alterations in metabolic flux, setting up a potential for endogenous lipotoxicity from saturated fatty acids after Myc inactivation. These results lead us to hypothesize that Myc directs metabolism in synergistic pathways to promote cell cycling and cell growth, and that loss of this integration is a cause of Myc oncogene addiction. We propose the following specific aims to address these hypotheses.
Specific Aim 1. To analyze changes in lipid raft composition during Myc-dependent cell cycle entry.
Specific Aim 2. To analyze the requirements for arachidonic acid metabolism during Myc-dependent cell cycle entry.
Specific Aim 3. To determine the role of lipotoxicity in Myc oncogene addiction. Together these studies have the potential to change current paradigms regarding control of signaling networks, to provide insight into proteins and miRNAs that participate in alteration of cell fates during programming of cells from quiescent to proliferative and tumorigenic states, and to reveal mechanisms underlying oncogene addiction.
The initiation and progression of cancer requires nutrient uptake to maintain cellular synthetic capacity and adaptation of cancer cells to a continually changing microenvironment. The systems biology approach we propose traces the interconnection of nutritional supply and lipid biosynthesis with regulation of genes, proteins, and metabolism, and may reveal mechanisms regulating cell growth signaling networks in proliferating cells and tumors.
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