Mesenchymal stem cells and macrophages interact through IL-6 to promote inflammatory breast cancer in pre-clinical models.

Adam R Wolfe,Jim M Reuben,Richard Larson,Khoi Chu,Naoto T Ueno,Brian Ruffell,Walter Hittelman,Michael Diehl,Wendy A Woodward,Nicholaus J Trenton,Bisrat G Debeb

doi:10.18632/oncotarget.12694

Abstract

Inflammatory breast cancer (IBC) is a unique and deadly disease with unknown drivers. We hypothesized the inflammatory environment contributes to the IBC phenotype. We used an in vitro co-culture system to investigate interactions between normal and polarized macrophages (RAW 264.7 cell line), bone-marrow derived mesenchymal stem cells (MSCs), and IBC cells (SUM 149 and MDA-IBC3). We used an in vivo model that reproduces the IBC phenotype by co-injecting IBC cells with MSCs into the mammary fat pad. Mice were then treated with a macrophage recruitment inhibitor, anti-CSF1. MSC and macrophages grown in co-culture produced higher levels of pro-tumor properties such as enhanced migration and elevated IL-6 secretion. IBC cells co-cultured with educated MSCs also displayed enhanced invasion and mammosphere formation and blocked by anti-IL-6 and statin treatment. The treatment of mice co-injected with IBC cells and MSCs with anti-CSF1 inhibited tumor associated macrophages and inhibited pSTAT3 expression in tumor cells. Anti-CSF1 treated mice also exhibited reduced tumor growth, skin invasion, and local recurrence. Herein we demonstrate reciprocal tumor interactions through IL-6 with cells found in the IBC microenvironment. Our results suggest IL-6 is a mediator of these tumor promoting influences and is important for the IBC induced migration of MSCs.

Highlights

Inflammatory breast cancer is a deadly variant of breast cancer that presents with skin changes on the breast and spreads rapidly as a local, diffuse, “brushfire” through the breast and adjacent tissue
The mesenchymal stem cells (MSCs) co-cultured with M2 macrophages migrated at an almost 2-fold increase on average compared to MSCs grown with serum alone, M0, or M1 macrophages (p < 0.05) (Figure 2A)
To investigate how MSCs cocultured with M2 macrophages impact MSC migration, we took MSC controls or MSC2-educated cells and transferred them to a co-culture system with two Inflammatory breast cancer (IBC) cell lines (SUM 149 or IBC3) for 24 hours

Summary

Introduction

Inflammatory breast cancer is a deadly variant of breast cancer that presents with skin changes on the breast and spreads rapidly as a local, diffuse, “brushfire” through the breast and adjacent tissue. These signs are caused in part by blockage of lymphatics and skin invasion, not by classic inflammation [1]. Our preliminary studies of non-tumor containing breast tissue at least 5 cm away from IBC tumor cells (normal adjacent tissue or the “field”) have identified interesting differences, . We hypothesized that the normal breast phenotype including, macrophage infiltration and resultant interactions with MSC, perhaps prior to tumor initiation, may contribute to the unusual presentation of IBC

Methods

Results

Conclusion