Poster abstracts
Poster number 110 submitted by Ashley Heinaman
Tumor cells survive loss of RasV12 expression through activation of autophagy
Ashley Heinaman (Molecular, Cellular, and Developmental Biology Program, The Ohio State University), Sathiya Manivannan (Department of Molecular & Human Genetics, Baylor College of Medicine ), Molly Josifov (Department of Molecular Genetics, The Ohio State University), Nanki Hura (Department of Molecular Genetics, The Ohio State University), Amanda Simcox (Department of Molecular Genetics, The Ohio State University)
Abstract:
Ras plays a role in many cellular processes including growth, survival, and differentiation. Abnormal function of Ras, which disrupts these critical cell processes, underlies many different human cancers. Common forms of cancer treatments may result in apparent tumor removal and an asymptomatic appearance, however there are often residual cancer cells that enter a period of dormancy and can lead to later relapse (1). Since these dormant cells are not actively proliferating, they evade common therapeutic agents that specifically target dividing cells, indicating a need for new cancer therapies. We have developed an inducible system in which we can manipulate RasV12 expression with a drug. When RasV12 is expressed, the cells proliferate. When RasV12 is switched off, the cells stop proliferating but remain viable and enter a dormant state. Our goal is to use this inducible-Ras cell culture model to identify genes required for regulating and maintaining tumor dormancy. RNA-sequencing revealed that dormant cells activate several genes that function in the autophagy pathway, a self-degradation process induced under metabolic stress to generate energy. I found that Atg5 and Lamp-1, required at the start and end of the autophagy pathway, were upregulated in the dormant cells. Blocking autophagy with an inhibitor, Bafilomycin, caused cell death only in the dormant cells, suggesting autophagy is important for their survival. AMPKα, an energy sensing kinase and known regulator of autophagy, is activated in the dormant cells (2,3). To functionally validate the role of AMPK, I will block its expression by RNAi or pharmacological inhibition (Compound C). I will also use inhibitors to evaluate the three upstream kinases (LKB1, CaMKK2, TAK1) known to phosphorylate and activate AMPKα. Discovering the signaling pathways activated in dormant tumor cells, which are critical for survival, will be the first step towards developing therapies that specifically target the dormant cells.
References:
1. Aguirre-Ghiso, J. A. Models, mechanisms and clinical evidence for cancer dormancy. Nat. Rev. Cancer 7, 834–846 (2007).
2. Alers, S., Loffler, A. S., Wesselborg, S. & Stork, B. Role of AMPK-mTOR-Ulk1/2 in the Regulation of Autophagy: Cross Talk, Shortcuts, and Feedbacks. Molecular and Cellular Biology 32, 2–11 (2012).
3. Mihaylova, M. M. & Shaw, R. J. The AMPK signalling pathway coordinates cell growth, autophagy and metabolism. Nat. Cell Biol. 13, 1016–1023 (2011).
Keywords: Dormant cancer cells, Autophagy, Ras