Chemotherapy Coupled to Macrophage Inhibition Induces T-Cell and B-Cell Infiltration and Durable Regression in Triple-Negative Breast Cancer

Authors

Swarnima Singh
Nigel Lee
Diego A Pedroza
Igor L Bado
Clark Hamor
Licheng Zhang
Sergio Aguirre
Jingyuan Hu
Yichao Shen
Yitian Xu
Yang Gao
Na Zhao
Shu-Hsia Chen
Ying-Wooi Wan
Zhandong Liu
Jeffrey T Chang
Daniel Hollern
Charles M Perou
Xiang H F Zhang
Jeffrey M Rosen

Publication Date

6-15-2022

Journal

Cancer Research

DOI

10.1158/0008-5472.CAN-21-3714

PMID

35442423

PMCID

PMC9219596

PubMedCentral® Posted Date

12-15-2022

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes

Keywords

Animals, B-Lymphocytes, Claudins, Cyclophosphamide, Humans, Macrophages, Mice, T-Lymphocytes, Cytotoxic, Triple Negative Breast Neoplasms, Tumor Microenvironment

Abstract

Immunosuppressive elements within the tumor microenvironment, such as tumor-associated macrophages (TAM), can present a barrier to successful anti-tumor responses by cytolytic T cells. Here we employed preclinical syngeneic p53 null mouse models of triple-negative breast cancer (TNBC) to develop a treatment regimen that harnessed the immunostimulatory effects of low-dose cyclophosphamide coupled with the pharmacologic inhibition of TAMs using either a small molecule CSF1R inhibitor or an anti-CSF1R antibody. This therapeutic combination was effective in treating several highly aggressive TNBC murine mammary tumor and lung metastasis models. Single cell RNA sequencing characterized tumor-infiltrating lymphocytes (TIL) including helper T cells and antigen-presenting B cells that were highly enriched in responders to combination therapy. In one model that exhibited long-term post-treatment tumor regression, high dimensional imaging techniques identified the close spatial localization of B220+/CD86+-activated B cells and CD4+ T cells in tertiary lymphoid structures that were present up to 6 weeks post-treatment. The transcriptional and metabolic heterogeneity of TAMs was also characterized in two closely related claudin-low/mesenchymal subtype tumor models with differential treatment responses. A murine TAM signature derived from the T12 model was highly conserved in human claudin-low breast cancers, and high expression of the TAM signature correlated with reduced overall survival in breast cancer patients. This TAM signature may help identify human claudin-low breast cancer patients that will benefit from the combination of cyclophosphamide and anti-CSF1R therapy. These studies illustrate the complexity of the tumor immune microenvironment and highlight different immune responses that result from rational immunotherapy combinations.