PROJECT SUMMARY
Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human cancers, with a 5-year overall survival
(OS) rate of 7% for metastatic disease and less than 20% for locally advanced disease. Benefit from current
therapies including chemoradiation and surgery is often modest and transient. The significant challenge in the
field is how to turn immunologically cold PDAC into hot tumors that respond to immune checkpoint blockade
(ICB) therapy. We recently showed that irreversible electroporation (IRE), a tumor ablative technique currently
used in the clinics, significantly sensitized PDAC to anti-PD-1 ICB, leading to long-term survival in ~40% mice in
an aggressive orthotopic PDAC model. The remarkable anti-PDAC activity was attributed to efficient induction
of immunogenic cell death and stromal perturbation in favor of tumor infiltration of CTLs. As part of an effort to
define approaches to further enhance the efficacy of IRE + anti-PD-1 combination against PDAC, we uncovered
novel immune suppressive mechanism through time-of-flight mass cytometry (CyTOF) immune profiling and
single cell RNAseq of PDACs, which showed significant infiltration of CXCR2-expressing myeloid suppressive
cells (MDSCs). Furthermore, we found that IRE collapsed glycolysis and oxidative phosphorylation (OxPhos)
while upregulated glutaminase and glutamate, suggesting glutaminolysis as a compensatory mechanism to
satisfy energy and biosynthesis needs of IRE-treated cells. These data, taken together with the known critical
role of MDSCs and heightened glutamine metabolism in immune suppression, the findings by others that the
anti-diabetic drugs metformin and phenformin fundamentally change the tumor metabolic program to sensitize
tumors to ICB therapy, and our preliminary findings that both IRE and Re-Phen, a newly developed analogue of
phenformin, downregulated the OxPhos pathway while displaying an opposite effect on glutamate production,
lead us to hypothesize that attenuation of the immunosuppressive TME by depletion of MDSCs or suppression
of glutaminolysis by Re-Phen potentiates IRE + ICB to further prolong overall survival and increase the rate of
durable response. To test our hypothesis, we will pursue the following specific aims: 1) To identify
immunosuppressive factors associated with long-term versus short-term response to IRE + ICB. We will use
CyTOF immune profiling, scRNAseq, and cytokine array analyses to fully characterize the impact of IRE in the
presence and absence of anti-PD-1 on the immunosuppressive TME. 2) To determine the extent to which
therapies directed at MDSCs potentiate IRE + ICB. 3) To determine the extent to which disruption of the
metabolic program by theranostic agent Re-Phen potentiates IRE + ICB. The findings from this project are
expected to reveal previously undefined roles of MDSCs and deregulated metabolic programming in immune
suppression in the context of combined IRE + ICB therapy. Success of this project will have exceptional impact
because it will offer a potentially effective therapy for PDAC.
