Syndecan-1 facilitates breast cancer metastasis to the brain
Although survival rates for patients with localized breast cancer have increased, patients with metastatic breast cancer still have poor prognosis. Understanding key factors involved in promoting breast cancer metastasis is imperative for better treatments. In this study, we investigated the role of syndecan-1 (Sdc1) in breast cancer metastasis.
To assess the role of Sdc1 in breast cancer metastasis, we silenced Sdc1 expression in the triple-negative breast cancer human MDA-MB-231 cell line and overexpressed it in the mouse mammary carcinoma 4T1 cell line. Intracardiac injections were performed in an experimental mouse metastasis model using both cell lines. In vitro transwell blood–brain barrier (BBB) and brain section adhesion assays were utilized to specifically investigate how Sdc1 facilitates brain metastasis. A cytokine array was performed to evaluate differences in the breast cancer cell secretome when Sdc1 is silenced.
Silencing expression of Sdc1 in breast cancer cells significantly reduced metastasis to the brain. Conversely, overexpression of Sdc1 increased metastasis to the brain. We found that silencing of Sdc1 expression had no effect on attachment of breast cancer cells to brain endothelial cells or astrocytes, but migration across the BBB was reduced as well as adhesion to the perivascular regions of the brain. Loss of Sdc1 also led to changes in breast cancer cell-secreted cytokines/chemokines, which may influence the BBB.
Taken together, our study demonstrates a role for Sdc1 in promoting breast cancer metastasis to the brain. These findings suggest that Sdc1 supports breast cancer cell migration across the BBB through regulation of cytokines, which may modulate the BBB. Further elucidating this mechanism will allow for the development of therapeutic strategies to combat brain metastasis.
KeywordsBreast cancer Brain metastasis Syndecan-1 Blood–brain barrier
- Sdc1 KD
- Sdc1 OE
Human epidermal growth factor receptor 2 positive
Triple-negative breast cancer
Dulbecco’s modified Eagle’s medium
Fetal bovine serum
Basement membrane extract
Analysis of variance
Immortalized human umbilical vein endothelial cells
Green fluorescent protein
Platelet endothelial cell adhesion molecule-1
Growth regulated oncogene-alpha
Intercellular adhesion molecule 1
Granulocyte colony-stimulating factor
Granulocyte-macrophage colony-stimulating factor
C–C motif chemokine ligand 5
Enzyme-linked immunosorbent assay
The cancer genome atlas
We thank Jamie Sturgill, Megan Bliss-Morrow, David Finkelstein, Emily Lanning, Kaia Schwartz, Debra Chen, Tong Zhou, and Majid Jahromi for technical assistance with experiments, Azeddine Atfi for critical review of the manuscript, and Deborah Hurtado and Nikhail Mittal (ACEA Biosciences) for their guidance with the xCELLigence System. Imaging, flow cytometry, and sequencing work were performed in part at the Northwestern University Center for Advanced Microscopy, Flow Cytometry Core, and Genomics Core generously supported by NCI CCSG P30 CA060553 awarded to the Robert H. Lurie Comprehensive Cancer Center. Services and products in support of the research project were generated by the Virginia Commonwealth University School of Nursing Biobehavioral Research Laboratory and Massey Cancer Center Flow Cytometry Shared Resource, Cancer Mouse Models Core Laboratory, and Microscopy Facility, supported, in part, with funding from NIH-NCI Cancer Center Support Grant P30 CA016059. This work was supported by the American Cancer Society RSG-123275-CSM.
Original idea and project development-JEK; acquisition of data-MRS, MP, NGV, SMW, MM, LM, CE, AA, SK, MS, MD, JS, MOI, JEK; analysis and interpretation of data-MRS, MP, NGV, SMW, MM, LM, CE, AA, SK, MS, MD, JS, MOI, JEK; writing-MRS, SMW, JEK. All authors have reviewed and approved this manuscript.
This work was financially supported by the American Cancer Society Research Scholar Grant ACS/RSG-123275-CSM.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
We declare that all work were performed in compliance with current U.S. laws and all animal experiments were conducted in accordance with a protocol approved by NU and VCU Institutional Animal Care and Use Committee. VCU IACUC Protocol AD10000943.
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