PROJECT SUMMARY
Cancer metabolic reprogramming is key for the adaptation of the tumors to their harsh microenvironments.
Elevated LD abundance in tumors is frequently detected and is being recognized as a common feature of their
rewired metabolism. Lipid droplets are multifaceted organelles that participate in crucial cellular functions
including metabolism, membrane synthesis and homeostasis, signaling, and protein trafficking. We and others
have shown that hypoxia stimulates LD accumulation and that forced depletion of LD stores impedes tumor
growth. In order to discover novel regulators of lipid droplet turnover, we performed a genome-wide loss of
function screen based on Crispr engineering. Edited cells were separated based on their LD abundance and
sequenced. Our approach identified GFPT1 (glutamine-fructose-6-phosphate transaminase 1) as a candidate
positive LD regulator. GFPT1 catalyzes the first and rate limiting step in hexosamine biosynthesis.
The hexosamine biosynthetic pathway uses a glycolytic intermediate and glutamine to produce UDP-GlcNAc
which is essential for O-GlcNACylation and glycosylation of proteins and other macromolecules. Flux through
the hexosamine pathway is regulated by oncogenic events, nutrient availability, and input from nutrient sensors
like AMPK. In turn, HBP impacts crucial signaling functions and metabolic processes. Cancers have elevated
HBP activity and gene expression and are dependent on this activity for survival, growth, and metastatic
dissemination. Broad range pharmacological inhibitors of the HBP have shown promising results as a therapeutic
approach, however, there are no HBP-directed cancer therapies currently approved. Our preliminary finding that
GFPT1 positively regulates lipid storage prompts us to hypothesize that concurrent inhibition of the HBP and
neutral lipid synthesis will result in more complete LD depletion and enhanced tumor control.
In aim 1 we will delineate the lipid metabolic processes impacted by genetic GFPT1 ablation or small molecule
inhibition of HBP in PDAC models in vitro. We will uncover nutritional requirements for LD turnover under
normoxia and hypoxia in the context of HBP inhibition and will quantify the toxicity of combined HBP- and lipid
metabolism inhibition. Further, we will mechanistically link GFPT1 and AMPK via post-translational modifications
during normoxic and hypoxic LD accumulation. In aim 2 we will evaluate the in vivo efficacy of HBP and metabolic
inhibitors in orthotopic PDAC models and will measure the impact of these new treatment schemes on tumor
microenvironmental characteristics. Successful completion of this proposal will uncover a new connection
between two cancer-promoting metabolic programs and will develop new chemotherapeutic paradigms for
cancer treatment.