Email updates

Keep up to date with the latest news and content from Molecular Cancer and BioMed Central.

Open Access Highly Accessed Research

Microvesicles secreted by macrophages shuttle invasion-potentiating microRNAs into breast cancer cells

Mei Yang12, Jingqi Chen1, Fang Su3, Bin Yu2, Fengxi Su1, Ling Lin14, Yujie Liu1, Jian-Dong Huang2* and Erwei Song1*

Author Affiliations

1 Breast Tumor Center, Sun-Yat-Sen Memorial Hospital, Sun-Yat-Sen University, Guangzhou, PR China

2 Department of Biochemistry, University of Hong Kong, Pokfulam, Hong Kong SAR, China

3 LIN BAI-XIN Research Center of Medicine, Sun-Yat-Sen Memorial Hospital, Sun-Yat-Sen University, Guangzhou, PR China

4 Department of Rheumatology, The First Affiliated Hospital, Shantou University Medical College, Shantou city, Guangdong, PR China

For all author emails, please log on.

Molecular Cancer 2011, 10:117  doi:10.1186/1476-4598-10-117

Published: 22 September 2011

Abstract

Background

Tumor-associated macrophages (TAMs) are alternatively activated cells induced by interleukin-4 (IL-4)-releasing CD4+ T cells. TAMs promote breast cancer invasion and metastasis; however, the mechanisms underlying these interactions between macrophages and tumor cells that lead to cancer metastasis remain elusive. Previous studies have found microRNAs (miRNAs) circulating in the peripheral blood and have identified microvesicles, or exosomes, as mediators of cell-cell communication. Therefore, one alternative mechanism for the promotion of breast cancer cell invasion by TAMs may be through macrophage-secreted exosomes, which would deliver invasion-potentiating miRNAs to breast cancer cells.

Results

We utilized a co-culture system with IL-4-activated macrophages and breast cancer cells to verify that miRNAs are transported from macrophages to breast cancer cells. The shuttling of fluorescently-labeled exogenous miRNAs from IL-4-activated macrophages to co-cultivated breast cancer cells without direct cell-cell contact was observed. miR-223, a miRNA specific for IL-4-activated macrophages, was detected within the exosomes released by macrophages and was significantly elevated in the co-cultivated SKBR3 and MDA-MB-231 cells. The invasiveness of the co-cultivated breast cancer cells decreased when the IL-4-activated macrophages were treated with a miR-223 antisense oligonucleotide (ASO) that would inhibit miR-223 expression. Furthermore, results from a functional assay revealed that miR-223 promoted the invasion of breast cancer cells via the Mef2c-β-catenin pathway.

Conclusions

We conclude that macrophages regulate the invasiveness of breast cancer cells through exosome-mediated delivery of oncogenic miRNAs. Our data provide insight into the mechanisms underlying the metastasis-promoting interactions between macrophages and breast cancer cells.