Pseudomonas aeruginosa PcrV Enhances the Nitric Oxide-Mediated Tumoricidal Activity of Tumor-Associated Macrophages via a TLR4/PI3K/AKT/mTOR-Glycolysis-Nitric Oxide Circuit

Hua Yu,Lu Jiang,Yuanyuan Li,Qian Dai,Jin Peng,Junzhi Xiong,Rong Xin,Kebin Zhang,Halei Sheng,Ying Bai,Jing Qiu,Le Zhang,Qian Chen,Xiaomei Hu,Qiaoqiao Li,Xingmin Wang,Hong Zhang,Xiaomei He,Defeng Li

doi:10.3389/fonc.2021.736882

Abstract

Tumor-associated macrophages (TAMs), which display a tumor-supportive M2 phenotype, are closely related to tumor growth and metastasis. The reprogramming of TAMs toward a tumoricidal M1 profile has emerged as an attractive strategy for cancer immunotherapy. In this study, we found that the intratumoral injection of PcrV protein, a component of the Pseudomonas aeruginosa type 3 secretion system, suppressed tumor growth and increased apoptosis, inducible nitric oxide synthase (iNOS) expression, and the percentage of M1-polarized TAMs in tumor tissues. Furthermore, the intratumoral injection of PcrV-primed macrophages exerted a similar tumoricidal effect. In vitro analyses revealed that PcrV reeducated TAMs toward an antitumoral M1 phenotype and augmented their nitric oxide (NO)-mediated cytotoxicity against cancer cells. Mechanistically, we found that these effects were dependent on the activation of Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)-mediated regulation of a PI3K/AKT/mTOR-glycolysis-NO feedback loop via direct interaction with TLR4. Collectively, these results revealed a potential role for PcrV in cancer immunotherapy through the targeting of TAM plasticity.

Highlights

Tumor-associated macrophages (TAMs) form the major component of the immune cell infiltrate in the tumor microenvironment (TME) and are correlated with tumor development and progression
We further found that PcrV-mediated TAM reprogramming potentiated their nitric oxide (NO)-mediated cytotoxicity against cancer cells, effects that were exerted through the activation of a PI3K/AKT/mTOR-glycolysis-NO feedback loop via direct interaction with Tolllike receptor 4 (TLR4)
Mediated cytotoxicity is associated with tissue apoptosis and the inhibition of tumor growth, we evaluated the levels of tumor cell apoptosis and the expression of the NO-generating enzyme— inducible nitric oxide synthase (iNOS)—in PcrV-treated tumor tissues

Summary

Introduction

Tumor-associated macrophages (TAMs) form the major component of the immune cell infiltrate in the tumor microenvironment (TME) and are correlated with tumor development and progression. Macrophages infiltrated in the immunosuppressive TME are generally induced into the tumor-supportive M2 phenotype These M2-like TAMs play roles in supporting tumor growth and metastasis and maintaining an immunosuppressive TME by generating a series of anti-inflammatory and protumoral cytokines and mediators [1]. As macrophages are highly heterogeneous and plastic, TAMs exposed to M1-associated stimuli can undergo a reversal from the protumoral M2 to the tumoricidal M1 phenotype. M1-like TAMs exert tumoricidal activity through the production of proinflammatory cytokines (e.g., TNFA and IL12), cytotoxic nitric oxide (NO), and reactive oxygen species (ROS) and the activation of Th1 immune responses via increasing the expression of associated major histocompatibility complex class I and class II (MHCI/II) and costimulatory molecules (CD86 and CD80) [2]. The reeducation of TAMs from an M2 to an M1 phenotype has emerged as an attractive strategy for cancer immunotherapy

Methods

Results

Conclusion