Research Project: Pancreatic ductal adenocarcinoma (PDAC) remains the fourth leading cause of cancer deaths worldwide with a median survival of less than one year. These poor treatment outcomes highlight the urgent need to improve our understanding of the mechanisms underlying tumor initiation, growth and metastasis and to leverage that understanding toward better therapeutic options. Chromatin remodeling proteins are frequently dysregulated in human cancers, yet little is known about how they control tumorigenesis. In preliminary studies, we uncover an epigenetic program mediated by the histone deacetylase Sirtuin 6 (SIRT6) that is critical for the suppression of PDAC. Using genetically-engineered mouse models (GEMMs) and human lines, we demonstrate that SIRT6 inactivation cooperates with oncogenic KRAS to drive PDAC progression and metastasis via upregulation of LIN28B, a negative regulator of the let-7 microRNA. SIRT6 loss results in histone 3 lysine 9 (H3K9) and lysine 56 (H3K56) hyperacetylation at the LIN28B promoter, MYC recruitment, and pronounced induction of LIN28B and of downstream LIN28B/let-7 targets. This epigenetic program defines a distinct subset of human PDAC characterized by reduced SIRT6 expression and exquisite dependence on LIN28B activation for tumor growth. Thus, we identify SIRT6 as an important PDAC tumor suppressor and uncover the LIN28B pathway as a potential therapeutic target in this molecularly- defined PDAC subset. In the experiments outlined in this proposal, we will investigate the specific roles of LIN28B in PDAC tumor biology and explore novel therapeutic approaches to target this molecularly-defined subset of LIN28B+ PDAC. Specifically, I propose to 1) Use my panel of molecularly characterized human cell lines and GEMMs to identify functionally relevant LIN28B/let-7 target genes in PDAC and explore the role of LIN28B in regulating fundamental cellular processes including cell cycle progression and metabolic pathways, 2) dissect the functional role of LIN28B in PDAC initiation and metastasis and 3) develop novel therapeutic approaches to target LIN28B directly in vivo. Career Goals: I am committed to a career in cancer research. As a graduate student in the laboratory of Dr. Larry Matherly, I gained expertise in one-carbon metabolism and membrane transport, molecular pharmacology and novel drug design and characterization. As a postdoctoral fellow in Dr. Raul Mostoslavsky's lab, I specialized in mouse models of pancreatic cancer, tumor metabolism and chromatin biology. My career goal is to obtain a tenure-track research faculty position at a leading cancer research institute where I can combine these two perspectives to study the role chromatin modifiers have in the epigenetic reprogramming of PDAC and exploit these findings to guide therapeutic discovery. Career Development and Environment: My successful transition to independence will be significantly enhanced by further scientific and career developmental training. With this in mind, I have assembled an outstanding mentoring team with complementary expertise for the K99 period of the award. Dr. Raul Mostoslavsky will act as primary mentor and I will be co-mentored by Dr. Nabeel Bardeesy. Dr. Mostoslavsky is an expert in chromatin biology and metabolism. Dr. Bardeesy is a widely recognized expert in pancreatic cancer pathogenesis and mouse models. To complement my mentorship committee I have put together a scientific advisory committee made up of Drs. Nick Dyson, Richard Gregory, Cyril Benes and Wilhelm Haas. Dr. Dyson is a world-renowned cancer biologist and expert in cell cycle control, Dr. Gregory is an expert on RNA biology and more specifically on the LIN28/let-7 axis, Dr. Benes has had many years of experience in novel therapeutic discovery and Dr. Haas has a depth of experience performing proteomic and metabolomics analysis. With their support, I have devised a research and training strategy to prepare me for independence. Their mentorship will allow me to develop key skills in quantitative and computational biology, in vitro and in vivo pancreatic cancer models, metabolomics and proteomics. Moreover, mentoring will emphasize career development training for which I will have both didactic course work and one-on-one mentoring sessions. The K99/R00 award would afford me the protected time needed for this advanced training and allow me to continue to foster my growth under the mentorship of Dr. Mostoslavsky and Dr. Bardeesy. I expect that the mentored phase of this proposal, which includes using cell lines and mouse models to investigate the role of LIN28B in pancreatic cancer will take 2 years and result in at least one major publication. The following independent phase of the award will allow me to identify and characterize novel therapeutic strategies of targeting LIN28B. Together these data will be used to justify future studies proposed in an R01 grant that I plan to submit at the start of the second year of the independent phase. The hosting institution, Massachusetts General Hospital Cancer Center, is at the leading edge of cancer research. It has unparalleled resources for laboratory research, excellent opportunities for training in career development and a collaborative scientific environment that excels the requirements to achieve my training goals. With all these resources in hand and support from the K99/R00 I will have every opportunity for success as an independent cancer researcher.
Pancreatic cancer is the fourth leading cause of cancer deaths worldwide and carries a prognosis of less than one year. Our preliminary data identifies a new pathway, which is critical for the growth and survival of a major subset of pancreatic cancers, characterized by high expression of the LIN28B protein. This research proposal is relevant to public health because it will explore the specific biologic roles of LIN28B in pancreatic cancer and identify novel approaches to block this pathway therapeutically.