Project Summary
It is widely accepted that tumors are highly heterogeneous. There is a subpopulation of cells in a tumor,
called tumor-initiating cell, that can be isolated and are able to self-renew, differentiate and form the bulk of the
tumor. Many cancers don't respond to traditional chemotherapy or radiotherapy, and those that initially
respond, often relapse. Conventional therapy only attacks proliferating cells, leaving behind a pool of resistant
stem-like cells that are able to regenerate the whole tumor. Understanding mechanisms that regulate tumor-
initiating activity will lead to designing and developing effective therapeutics. Our lab has demonstrated for the
first time that the nutrient sensor O-GlcNAc transferase (OGT) regulates cancer-initiating cells in vitro and in
vivo. Reducing OGT, genetically or pharmacologically, blocks mammosphere formation in vitro and reduced
epithelial-mesechymal markers (EMT), cancer stem cell markers. Importantly, overexpression of OGT, in
multiple breast cancer cells, increases cancer stem cell markers including NANOG, increases mammosphere
formation in vitro and increases tumor initiation in vivo. In this proposal, we hope to uncover molecular
mechanism by which OGT regulates tumor initiation, by in part, understanding OGT interactome and O-
GlcNAcome in breast cancer tumor initiating cells. This information will allow us to identify novel therapeutic
targets in treating cancer and reverse drug resistance. Based on our preliminary results, the central hypothesis
of this application is that the nutrient sensor O-GlcNAc transferase plays a fundamental role in breast cancer
initiating cells via, in part, NANOG regulation. Completion of these experiments will contribute to our
understanding of how nutrient-sensing pathways connects at the molecular level to self-renewing cancer stem
cells (CSCs) and providing a framework for understanding how cancer alterations in metabolic pathways
regulate core self-renewal signaling that controls CSC maintenance. In Aim #1, we will determine the
molecular basis of OGT/O-GlcNAc regulation of the master CSC regulator NANOG. This aim will determine the
molecular basis of OGT regulation of NANOG in breast cancer tumor initiating cells. In Aim #2, we will Identify
OGT interactome/O-GlcNAcome between between cancer cells and cancer stem cells. This aim will identify
OGT interacting proteins and O-GlcNAcylated protein in tumor initiating cells to identify novel pathways and
regulators of tumor-initiating ability. The final aim will evaluate the role of OGT in regulating tumor-initiating
activity in vivo. Importantly, we will test novel OGT inhibitors in preclinical cancer models and test whether
OGT targeting drugs as potential anti-tumor initiation cell therapeutic strategy against breast cancer growth
and metastasis in vivo. These studies will further our understanding of how metabolic reprogramming in cancer
cells connects at the molecular level to tumor initiating cells and will create mechanistic understanding of how
nutrient sensor OGT can couple to cancer initiation pathways and establish OGT as therapeutic target for
treatment of resistant cancers.