Project Summary Abstract
Alteration of essential metabolic pathways is a major mechanism by which oncogenic KRAS promotes tumor
development and growth in pancreatic ductal adenocarcinoma (PDAC). KRAS-driven PDAC is dependent on
macropinocytosis (MP) and autophagy to fuel the high metabolic demand of rapid proliferation. Thus, these
metabolic processes are attractive targets for the development of treatments for PDAC. Genetic depletion of
KRAS results in downregulation of MP in PDAC. Additionally, our lab demonstrated that KRAS depletion or
inhibition of ERK-MAPK signaling decreased glucose uptake and glycolysis but increased autophagy, thereby
enhancing dependency on autophagy for essential nutrient supply. Accordingly, dual RAS-pathway and
autophagy inhibition via chloroquine (CQ) synergistically enhanced efficacy in PDAC. Clinical data demonstrated
that resistance to this treatment arises over time through unknown mechanisms. Preliminary data indicates that
following RAS or ERK inhibition, both autophagy induction and MP downregulation are transient—with
autophagic and MP activity returning to/surpassing basal levels after prolonged treatment. Recent work has
suggested that these nutrient scavenging processes are able to compensate for loss of each other. We
demonstrate an inverse temporal relationship between autophagy and MP following depletion or inhibition of the
KRAS-ERK MAPK pathway. Furthermore, we show that CQ, commonly thought to inhibit lysosomal acidification,
does not prevent degradation of MP-derived proteins. We hypothesize that there is compensatory regulation
between autophagy and MP in the context of RAS-pathway inhibition. Thus, during prolonged RAS-pathway and
autophagy inhibitor treatment, PDAC cells upregulate MP, consequently abrogating dependency on autophagy
and reducing sensitivity to autophagy inhibition. Aim 1 will test the hypothesis that upregulation of MP confers
resistance to dual autophagy and RAS-pathway inhibition in vitro and in vivo. Additionally, we present the
unexpected observation that prolonged inhibition of the ERK-MAPK pathway results in the upregulation of MP.
Previous PDAC studies have employed genetic depletion of KRAS to demonstrate the role of oncogenic KRAS
in driving MP with no evaluation of inhibitors of KRAS or the ERK-MAPK pathway. Given the dependence of
PDAC on macropinocytic uptake for tumorigenic growth, it is imperative to understand how these inhibitors
regulate MP. Initial Aim 2 studies will be dedicated to comprehensive characterization of MP regulation in the
context of genetic and pharmacological inhibition of KRAS and ERK over time. Subsequent work in Aim 2 will
determine whether the changes in MP via RAS-pathway inhibition corresponds with changes in uptake and
efficacy of nab-paclitaxel. Further understanding of RAS-driven regulation of these essential metabolic pathways
in PDAC will inform future development of RAS-pathway inhibitor combinations. These studies will require my
application of a diverse spectrum of experimental approaches, advance my understanding of key steps in anti-
cancer therapeutic development, and foster my career development as an independent cancer researcher.