Blocking NHE1 stimulates glioma tumor immunity by restoring OXPHOS function of myeloid cells

Abstract

Background: Immunosuppressive tumor microenvironment (TME) in glioblastoma (GBM) is one of the contributing factors for failed immunotherapies. Therefore, there is an urgent need to better understand TME and to identify novel modulators of TME for more effective GBM therapies. We hypothesized that H + extrusion protein Na/H exchanger 1 (NHE1) plays a role in dysregulation of glucose metabolism and immunosuppression of GBM. We investigated the efficacy of blockade of NHE1 activity in combination with temozolomide (TMZ) therapy in increasing anti-tumor immunity. Methods: Mouse syngeneic intracranial glioma model was used to test four treatment regimens: DMSO (Vehicle-control), TMZ, NHE1 specific inhibitor HOE642, or TMZ+HOE642 (T+H) combination. Ex vivo 1 H/ 19 Fluorine magnetic resonance imaging (MRI) with cell tracking agent Vsense was performed to monitor the infiltration of glioma-associated microglia/myeloid cells (GAMs). Glucose metabolism and transcriptome profiles were analyzed by Seahorse analyzer and bulk RNA-sequencing. The impact of selective Nhe1 deletion in GAMs on sensitivity to anti-PD-1 therapy was evaluated in transgenic NHE1 knockout ( KO ) mice. Results: Among the tested treatment regimens, the T+H combination therapy significantly stimulated the infiltration of GAMs and T-cells; up-regulated Th1 activation, and mitochondrial oxidative phosphorylation (OXPHOS) pathway genes, increased glucose uptake and mitochondrial mass, and decreased aerobic glycolysis in GAMs. Selective deletion of Nhe1 in Cx3cr1 + Nhe1 KO mice increased anti-tumor immunity and sensitivity to TMZ plus anti-PD-1 combinatorial therapy. Conclusions: NHE1 plays a role in developing glioma immunosuppressive TME in part by dysregulating glucose metabolism of GAMs and emerges as a therapeutic target for improving glioma immunity.

Elevated microglial oxidative phosphorylation and phagocytosis stimulate post-stroke brain remodeling and cognitive function recovery in mice

“…Bulk RNA sequencing and bioinformatic analysis were performed in P2RY12 + microglia samples sorted by MACS and paired-end sequenced in the platform of Illumina HiSeq X, as in our recent report 82 . Briefly, the library was prepared using the SMARTer stranded total RNA pico V2 kit (Takara Bio, USA).…”

“…Mitochondrial stress tests were performed using Seahorse extracellular flux analyzer (Agilent Technologies) per the manufacturer’s instruction, as we reported recently 82 . P2RY12 + microglial cells were isolated from 3-day poststroke brain tissues using MACS, as described above.…”

The Role of Myeloid Cells in GBM Immunosuppression

“…It has been previously recognized that GAMs undergo constant epigenetic and metabolic reprogramming regarding oxidative phosphorylation and anaerobic glycolysis, swinging between pro- and anti-inflammatory responses for growth-promoting or tumor-killing activity ( 51 – 54 ). Anti-inflammatory GAMs use the tricarboxylic acid (TCA) cycle in mitochondria to produce electrons that are essential for oxidative phosphorylation of glucose to generate high amounts of adenosine triphosphate (ATP) ( 55 ).…”

DNA Damage Repair in Brain Tumor Immunotherapy

“…focused on the effect of Na/H exchanger 1 in combination with TMZ on immunotherapy. They found that NHE1 was closely related to the immunosuppressive TME of GBM, which is one of the reasons for downregulating the sensitivity of GBM to the immune response ( 150 ). And further validated the effect of combination treatment of NHE1 inhibitor HOE642 with TMZ on PD-1.…”