Aromatic secondary amine-functionalized fluorescent NO probes: improved detection sensitivity for NO and potential applications in cancer immunotherapy studies.

Yingying Huo,Juanjuan Wang,Junfeng Miao,Junru Fang,Wei Guo,Hu Shi

doi:10.1039/c8sc03694b

Abstract

Tumor-associated macrophages (TAMs), constituting up to 50% of the solid tumor mass and commonly having a pro-tumoral M2 phenotype, are closely associated with decreased survival in patients. Based on the highly dynamic properties of macrophages, in recent years the repolarization of TAMs from pro-tumoral M2 phenotype to anti-tumoral M1 phenotype by various strategies has emerged as a promising cancer immunotherapy approach for improving cancer therapy. Herein, we present an aromatic secondary amine-functionalized Bodipy dye 1 and its mitochondria-targetable derivative Mito1 as fluorescent NO probes for discriminating M1 macrophages from M2 macrophages in terms of their difference in inducible NO synthase (iNOS) levels. The two probes possess the unique ability to simultaneously respond to two secondary oxides of NO, i.e., N2O3 and ONOO-, thus being more sensitive and reliable for reflecting intracellular NO than most of the existing fluorescent NO probes that usually respond to N2O3 only. With 1 as a representative, the discrimination between M1 and M2 macrophages, evaluation of the repolarization of TAMs from pro-tumoral M2 phenotype to anti-tumoral M1 phenotype, and visualization of NO communication during the immune-mediated phagocytosis of cancer cells by M1 macrophages have been realized. These results indicate that our probes should hold great potential for imaging applications in cancer immunotherapy studies and relevant anti-cancer drug screening.

Highlights

Macrophages are specialized immune cells found all over the body that exist primarily to engulf and digest cellular debris, foreign substances, microbes, and cancer cells in a process called phagocytosis
The two probes possess the unique ability to simultaneously respond to two secondary oxides of nitric oxide (NO), i.e., N2O3 and ONOOÀ, being more sensitive and reliable for reflecting intracellular NO than most of the existing fluorescent NO probes that usually respond to N2O3 only
With 1 as a representative, the discrimination between M1 and M2 macrophages, evaluation of the repolarization of Tumor-associated macrophages (TAMs) from pro-tumoral M2 phenotype to anti-tumoral M1 phenotype, and visualization of NO communication during the immune-mediated phagocytosis of cancer cells by M1 macrophages have been realized. These results indicate that our probes should hold great potential for imaging applications in cancer immunotherapy studies and relevant anti-cancer drug screening

Summary

Introduction

Macrophages are specialized immune cells found all over the body that exist primarily to engulf and digest cellular debris, foreign substances, microbes, and cancer cells in a process called phagocytosis. Edge Article dynamic process and the phenotype of M1- or M2-polarized macrophages can be reversed depending on the microenvironmental cues they receive.[8] For instance, the reversion of macrophages from M2 phenotype to M1 phenotype and reduction of immunosuppressive effects from the M2 population have been observed when TAMs were treated with interferon-g/lipopolysaccharide (IFN-g/LPS);[9,10] in patients with extended survival, the M1 macrophages account for the majority of macrophages present within tumors,[11] distinct from the cases in tumor development and metastasis, where macrophages predominantly exhibit a pro-tumoral M2 phenotype.[2,3,4,5,6,7] Based on these discoveries, the repolarization of TAMs from M2 phenotype to M1 phenotype to activate their anti-tumoral potential by various strategies has emerged as an attractive and promising approach in cancer immunotherapy in recent years.[2,12,13,14,15,16,17] In this context, the development of efficient methods that can discriminate M1 macrophages from M2 macrophages is of crucial guiding signi cance for cancer immunotherapy studies and relevant anti-cancer drug screening.

Results

Conclusion