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Updated: Jul 24, 2025
Studying the Role of Alveolar Macrophages in Breast Cancer Metastasis
Published on: June 26, 2016
Rac and Cdc42 inhibitors reduce macrophage function in breast cancer preclinical models
Anamaris Torres-Sanchez1,2, Michael Rivera-Robles2, Linette Castillo-Pichardo2
1Department of Biology, University of Puerto Rico, San Juan, Puerto Rico.
Background:
Metastatic disease lacks effective treatments and remains the primary cause of mortality from epithelial cancers, especially breast cancer. The metastatic cascade involves cancer cell migration and invasion and modulation of the tumor microenvironment (TME). A viable anti-metastasis strategy is to simultaneously target the migration of cancer cells and the tumor-infiltrating immunosuppressive inflammatory cells such as activated macrophages, neutrophils, and myeloid-derived suppressor cells (MDSC). The Rho GTPases Rac and Cdc42 are ideal molecular targets that regulate both cancer cell and immune cell migration, as well as their crosstalk signaling at the TME. Therefore, we tested the hypothesis that Rac and Cdc42 inhibitors target immunosuppressive immune cells, in addition to cancer cells. Our published data demonstrate that the Vav/Rac inhibitor EHop-016 and the Rac/Cdc42 guanine nucleotide association inhibitor MBQ-167 reduce mammary tumor growth and prevent breast cancer metastasis from pre-clinical mouse models without toxic effects.
Methods:
The potential of Rac/Cdc42 inhibitors EHop-016 and MBQ-167 to target macrophages was tested in human and mouse macrophage cell lines via activity assays, MTT assays, wound healing, ELISA assays, and phagocytosis assays. Immunofluorescence, immunohistochemistry, and flow cytometry were used to identify myeloid cell subsets from tumors and spleens of mice following EHop-016 or MBQ-167 treatment.
Results:
EHop-016 and MBQ-167 inhibited Rac and Cdc42 activation, actin cytoskeletal extensions, migration, and phagocytosis without affecting macrophage cell viability. Rac/Cdc42 inhibitors also reduced tumor- infiltrating macrophages and neutrophils in tumors of mice treated with EHop-016, and macrophages and MDSCs from spleens and tumors of mice with breast cancer, including activated macrophages and monocytes, following MBQ-167 treatment. Mice with breast tumors treated with EHop-016 significantly decreased the proinflammatory cytokine Interleukin-6 (IL-6) from plasma and the TME. This was confirmed from splenocytes treated with lipopolysaccharide (LPS) where EHop-016 or MBQ-167 reduced IL-6 secretion in response to LPS.
Conclusion:
Rac/Cdc42 inhibition induces an antitumor environment via inhibition of both metastatic cancer cells and immunosuppressive myeloid cells in the TME.
Insights
Rac and Cdc42 inhibitors EHop-016 and MBQ-167 reduce breast cancer growth and metastasis by targeting both cancer cells and immunosuppressive myeloid cells in the tumor microenvironment (TME). These inhibitors create an antitumor environment without toxic effects.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Metastatic epithelial cancers, particularly breast cancer, lack effective treatments and are a leading cause of mortality.
- The metastatic cascade involves cancer cell migration, invasion, and tumor microenvironment (TME) modulation.
- Targeting cancer cell migration and immunosuppressive immune cells offers a viable anti-metastasis strategy.
Purpose of the Study:
- To test the hypothesis that Rac and Cdc42 inhibitors target immunosuppressive immune cells alongside cancer cells.
- To evaluate the efficacy of EHop-016 and MBQ-167 in preclinical models of breast cancer metastasis.
Main Methods:
- Assessed Rac/Cdc42 inhibitor effects on macrophage cell lines using activity, MTT, wound healing, ELISA, and phagocytosis assays.
- Utilized immunofluorescence, immunohistochemistry, and flow cytometry to analyze myeloid cell subsets in treated mouse models.
- Measured plasma and TME levels of Interleukin-6 (IL-6) in treated mice.
Main Results:
- EHop-016 and MBQ-167 inhibited Rac/Cdc42 activation, migration, and phagocytosis in macrophages without impacting cell viability.
- Inhibitors reduced tumor-infiltrating macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs) in treated mice.
- Treatment with EHop-016 significantly decreased pro-inflammatory IL-6 levels in plasma and the TME.
Conclusions:
- Rac/Cdc42 inhibition effectively targets both metastatic cancer cells and immunosuppressive myeloid cells within the TME.
- These inhibitors promote an antitumor environment, offering a novel therapeutic strategy for metastatic breast cancer.
- EHop-016 and MBQ-167 demonstrate potential as anti-metastasis agents with no observed toxic effects in preclinical models.
