Emodin suppresses pulmonary metastasis of breast cancer accompanied with decreased macrophage recruitment and M2 polarization in the lungs.

Abstract

Breast cancer is the leading cause of death in female cancer patients due to the lack of effective treatment for metastasis. Macrophages are the most abundant immune cells in the primary and metastatic tumors, and contribute to tumor initiation, progression, and metastasis. Emodin has been found to exert anti-tumor effects through promoting cell cycle arrest and apoptosis, and inhibiting angiogenesis, but its effects on tumor-associated macrophages during cancer metastasis have not been investigated. Mice inoculated with 4T1 or EO771 breast cancer cells orthotopically were treated with Emodin after the primary tumors reached 200 mm3 in size. Primary tumor growth, lung metastasis, and macrophage infiltration in the lungs were analyzed. In vitro experiments were performed to examine the effects of Emodin on macrophage migration and M2 polarization, and the underlying mechanisms. Emodin significantly suppressed breast cancer lung metastasis in both orthotopic mouse models without apparent effects on primary tumors. Reduced infiltration of F4/80+ macrophages and Ym1+ M2 macrophages in lungs was observed in Emodin-treated mice. In vitro experiments demonstrated that Emodin decreased the migration of macrophages toward tumor cell-conditioned medium (TCM) and inhibited macrophage M2 polarization induced by TCM. Mechanistically, Emodin suppressed STAT6 phosphorylation and C/EBPβ expression, two crucial signaling events in macrophage M2 polarization, in macrophages treated with IL-4 or TCM. Taken together, our study, for the first time, demonstrated that Emodin suppressed pulmonary metastasis of breast cancer probably through inhibiting macrophage recruitment and M2 polarization in the lungs by reducing STAT6 phosphorylation and C/EBPβ expression.

• Authors: Xuemei Jia, Fang Yu, Junfeng Wang, Stephen Iwanowycz, Fatma Saaoud, Yuzhen Wang, Jun Hu, Qian Wang, Daping Fan
• Journal: Breast cancer research and treatment (Breast Cancer Res Treat) Vol. 148 Issue 2 Pg. 291-302 (Nov 2014) ISSN: 1573-7217 [Electronic] Netherlands
• PMID: 25311112 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Culture Media, Conditioned
• Protein Kinase Inhibitors
• RNA, Messenger
• STAT6 Transcription Factor
• Stat6 protein, mouse
• Emodin

Topics

• Animals
• Apoptosis (drug effects)
• Blotting, Western
• Breast Neoplasms (metabolism, pathology, prevention & control)
• Cell Adhesion (drug effects)
• Cell Movement (drug effects)
• Cell Proliferation (drug effects)
• Culture Media, Conditioned (pharmacology)
• Emodin (therapeutic use)
• Female
• Humans
• Lung Neoplasms (metabolism, prevention & control, secondary)
• Macrophages (drug effects, metabolism, pathology)
• Mice
• Mice, Inbred BALB C
• Mice, Inbred C57BL
• Mice, Nude
• Protein Kinase Inhibitors (therapeutic use)
• RNA, Messenger (genetics)
• Real-Time Polymerase Chain Reaction
• Reverse Transcriptase Polymerase Chain Reaction
• STAT6 Transcription Factor (genetics, metabolism)
• Signal Transduction
• Tumor Cells, Cultured
• Xenograft Model Antitumor Assays