Page 34 - WNS 2024 e-Program - Resized and Binded

Modulation of Glycolytic Shunting in Myeloid Cells Via Heme
Oxygenase-1 Pathway Results in Enhanced T Cell Activation and
Improved Survival in a Murine Glioma Model
Lily H. Kim, MD; Department of Neurosurgery, Stanford University School
of Medicine
John Choi, MD, MEd; Ryan Nitta, PhD; Ayush Pant, BS; Ethan Schonfeld,
BS; Gordon Li, MD; Christina Jackson, MD; Xinnan Wang, MD, PhD;
Michael Lim, MD; Department of Neurosurgery, Stanford University School
of Medicine

Introduction: Cancer cells preferentially utilize aerobic glycolysis
(Warburg effect). Recent studies show similar metabolic reprogramming in
immune cells of the tumor microenvironment (TME). Heme oxygenase-1
(HMOX-1), a metabolic regulatory gene, is known to be upregulated in
glioblastoma (GBM) myeloid cells, but how HMOX-1 specifically modulates
immunosuppression and energy utilization remains poorly understood. We
aimed to investigate the effect of HMOX-1 downregulation in GBM TME on
immune response and energy metabolism.
Methods: Syngeneic glioma models with C57BL/6J mice implanted with
CT-2A cells were treated with intracranial (IC) injection of the HMOX-1
inhibitor zinc protoporphyrin (ZnPP), intraperitoneal (IP) injection of anti-
PD-1, IC ZnPP + IP anti-PD-1, or IC saline (sham). Adoptive cell transfer of
myeloid-derived suppressor cells (MDSCs) with siRNA knockdown of Hmox-
1 into CSF-1R myeloid-depleted mice were used for mechanistic studies.
Changes in glycolytic energy dynamics were assessed with the Seahorse
mitochondrial stress test. Immunophenotyping was performed with flow
cytometry.
Results: Myeloid Hmox-1 knockdown as well as HMOX-1 inhibition with
ZnPP resulted in increased T cell activation with a significantly higher IFN-γ
expression in brain compared to non-treated mice (P = 0.039, 0.02,
respectively). However, there was also a compensatory upregulation of PD-
L1 in myeloid cells with ZnPP treatment (P < 0.0001). ZnPP monotherapy
and combination therapy with anti-PD-1 + ZnPP led to improved median
overall survival compared to sham and anti-PD-1 monotherapy arms, with
combination therapy demonstrating the greatest survival benefit (P <
0.0001). Metabolic assays for both ZnPP treatment and Hmox-1 knockdown
demonstrated a shift away from glycolysis-predominant metabolism in
MDSCs, indicating a change in energy dynamics from the usual TME.

Conclusions: HMOX-1 inhibition enhanced T cell activation, shifted
MDSCs away from cancer cell-like glycolytic shunting, and improved
survival in a murine glioma model. Modulation of metabolic reprogramming
can have an anti-tumor, immune-activating effect that synergizes with
checkpoint inhibition.
Figure 1.