Biologically driven cut-off definition of lymphocyte ratios in metastatic breast cancer and association with exosomal subpopulations and prognosis

Lorenzo Gerratana,Maria Grazia Vitale,Michele Bartoletti,Alessandro Magini,Gianpiero Fasola,Carla Di Loreto,C Lisanti ,Barbara Toffoletto,Carla Emiliani,Michela Bulfoni,Loredana Casalis,Marta Ruiz Lera ,Alessandro Marco Minisini,Silvia Zago,Daniela Cesselli,Federica Caponnetto,Francesco Curcio,Giacomo Pelizzari,Pietro Parisse,Antonio Paolo Beltrami,Marta Bonotto,Valentina Fanotto,Debora Basile,Fabio Puglisi

doi:10.1038/s41598-020-63291-2

Abstract

High neutrophil to lymphocyte ratio (NLR) and monocyte to lymphocyte ratio (MLR) are respectively associated with systemic inflammation and immune suppression and have been associated with a poor outcome. Plasmatic exosomes are extracellular vesicles involved in the intercellular communication system that can exert an immunosuppressive function. Aim of this study was to investigate the interplay between the immune system and circulating exosomes in metastatic breast cancer (MBC). A threshold capable to classify patients according to MLR, NLR and PLR, was computed through a receiving operator curve analysis after propensity score matching with a series of female blood donors. Exosomes were isolated from plasma by ExoQuick solution and characterized by flow-cytometry. NLR, MLR, PLR and exosomal subpopulations potentially involved in the pre-metastatic niche were significantly different in MBC patients with respect to controls. MLR was significantly associated with number of sites at the onset of metastatic disease, while high levels of MLR and NLR were found to be associated with poor prognosis. Furthermore, exosomal subpopulations varied according to NLR, MLR, PLR and both were associated with different breast cancer subtypes and sites of distant involvement. This study highlights the nuanced role of immunity in MBC spread, progression and outcome. Moreover, they suggest potential interaction mechanisms between immunity, MBC and the metastatic niche.

Highlights

The role played by the immune system in cancer pathophysiology is central[1]
Circulating monocytes could be recruited at tumor site and differentiate into macrophages, where they are further involved in tumor development, dissemination, angiogenesis, matrix degradation, and immunosuppression; whereas lymphopenia could be linked to a weak anti-tumor response and lower tumor-infiltrating lymphocytes[10,11]
We have previously shown that in glioblastoma patients, plasma-derived exosomes were able to reduce the proliferation of T lymphocyte and that this effect was mediated by CD14 + monocytes[28]

Summary

Introduction

The role played by the immune system in cancer pathophysiology is central[1]. According to the immunoediting theory, it plays a dual function, by both protecting the organism against cancer and, on the other hand, facilitating cancer’s escape and promoting its progression[2]. Exosomes released by an activated tumor microenvironment can increase tumor aggressiveness and immune-escape[24,25] In this regard, all Antigen Presenting Cells (APCs) are profoundly affected by tumor derived exosomes (TDE), that impair the capacity of circulating CD14 + monocytes to differentiate into functional DCs, and lower or disable their expression of HLA-DR24,26. All Antigen Presenting Cells (APCs) are profoundly affected by tumor derived exosomes (TDE), that impair the capacity of circulating CD14 + monocytes to differentiate into functional DCs, and lower or disable their expression of HLA-DR24,26 These altered cells suppress lymphocyte proliferation and impair the expression of effector molecules such as IFN-γ and perforin, to what is observed among natural killer cells[24,27]. The prognostic role of LRs was investigated both singularly and after their combination

Objectives

Methods

Results

Discussion

Conclusion