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

Cancer Res. 2022 Jun 15;82(12):2281-2297. doi: 10.1158/0008-5472.CAN-21-3714.


Immunosuppressive elements within the tumor microenvironment, such as tumor-associated macrophages (TAM), can present a barrier to successful antitumor 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 including Th cells and antigen-presenting B cells that were highly enriched in responders to combination therapy. In one model that exhibited long-term posttreatment 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 posttreatment. 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 patients with breast cancer. This TAM signature may help identify human patients with claudin-low breast cancer 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.

Significance: Immunostimulatory chemotherapy combined with pharmacologic inhibition of TAMs results in durable treatment responses elicited by Th cells and B cells in claudin-low TNBC models.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • B-Lymphocytes
  • Claudins / metabolism
  • Claudins / therapeutic use
  • Cyclophosphamide / pharmacology
  • Cyclophosphamide / therapeutic use
  • Humans
  • Macrophages / metabolism
  • Mice
  • T-Lymphocytes, Cytotoxic / pathology
  • Triple Negative Breast Neoplasms* / pathology
  • Tumor Microenvironment


  • Claudins
  • Cyclophosphamide