Am80-GCSF synergizes myeloid expansion and differentiation to generate functional neutrophils that reduce neutropenia-associated infection andmortality.

Lin Li,Siyue Lou,Qiaojun He,Sajad Khazal,Xiaotian Qi,Hiroyuki Shimada,Koichi Shudo,Weili Sun,Alice Zhou,Hisham Abdel‐Azim,Hong Zhu,Lingtao Wu,Nemani V Prasadarao,David Warburton,Yong‐Mi Kim

doi:10.15252/emmm.201606434

Abstract

Neutrophils generated by granulocyte colony‐stimulating factor (GCSF) are functionally immature and, consequently, cannot effectively reduce infection and infection‐related mortality in cancer chemotherapy‐induced neutropenia (CCIN). Am80, a retinoic acid (RA) agonist that enhances granulocytic differentiation by selectively activating transcription factor RA receptor alpha (RARα), alternatively promotes RA‐target gene expression. We found that in normal and malignant primary human hematopoietic specimens, Am80‐GCSF combination coordinated proliferation with differentiation to develop complement receptor‐3 (CR3)‐dependent neutrophil innate immunity, through altering transcription of RA‐target genes RARβ2, C/EBPε, CD66,CD11b, and CD18. This led to generation of functional neutrophils capable of fighting infection, whereas neutralizing neutrophil innate immunity with anti‐CD18 antibody abolished neutrophil bactericidal activities induced by Am80‐GCSF. Further, Am80‐GCSF synergy was evaluated using six different dose‐schedule‐infection mouse CCIN models. The data demonstrated that during “emergency” granulopoiesis in CCIN mice undergoing transient systemic intravenous bacterial infection, Am80 effect on differentiating granulocytic precursors synergized with GCSF‐dependent myeloid expansion, resulting in large amounts of functional neutrophils that reduced infection. Importantly, extensive survival tests covering a full cycle of mouse CCIN with perpetual systemic intravenous bacterial infection proved that without causing myeloid overexpansion, Am80‐GCSF generated sufficient numbers of functional neutrophils that significantly reduced infection‐related mortality in CCIN mice. These findings reveal a differential mechanism for generating functional neutrophils to reduce CCIN‐associated infection and mortality, providing a rationale for future therapeutic approaches.

Highlights

cancer chemotherapy-induced neutropenia (CCIN) is a condition in which the number of neutrophils in patients’ bloodstream is decreased, leading to increased susceptibility to microbial infections
In this study, whether and how Am80 can synergistically work with granulocyte colony-stimulating factor (GCSF) during granulopoiesis to generate sufficient numbers of functional neutrophils while preventing myeloid overexpansion
We find that Am80-GCSF sustains active proliferation in normal primary human hematopoietic precursors while inhibiting leukemic growth in primary human acute myeloid leukemia (AML) specimens

Summary

Introduction

CCIN is a condition in which the number of neutrophils in patients’ bloodstream is decreased, leading to increased susceptibility to microbial infections. Recent studies show that Am80 can induce modest production of neutrophils displaying significantly higher bactericidal activity in vitro, compared to those induced by GCSF (Ding et al, 2013) This raises question: Could Am80-GCSF combination serve as a novel synergist, acting through differential mechanisms by synchronizing Am80’s competence for promoting neutrophil differentiation with GCSF’s profound capability for myeloid expansion, to induce sufficient numbers of functional neutrophils fighting infection?. Using different human granulopoietic systems and mouse CCIN models, our study reveals a novel Am80-GCSF synergy that can induce large amounts of functional neutrophils to reduce CCIN-associated infection and mortality while preventing myeloid overexpansion This is likely through altering transcription of RA-target genes that promote differentiation of GCSF-expanded granulocytic precursors into functional neutrophils with well-developed CR3 immunity

Results

Discussion