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Updated: Jun 20, 2026
Generating a Murine Orthotopic Metastatic Breast Cancer Model and Performing Murine Radical Mastectomy
Published on: November 29, 2018
miR-200 enhances mouse breast cancer cell colonization to form distant metastases
Derek M Dykxhoorn1, Yichao Wu, Huangming Xie
1Department of Pediatrics, Immune Disease Institute, Harvard Medical School, Boston, Massachusetts, United States of America. ddykxhoorn@med.miami.edu
Background:
The development of metastases involves the dissociation of cells from the primary tumor to penetrate the basement membrane, invade and then exit the vasculature to seed, and colonize distant tissues. The last step, establishment of macroscopic tumors at distant sites, is the least well understood. Four isogenic mouse breast cancer cell lines (67NR, 168FARN, 4TO7, and 4T1) that differ in their ability to metastasize when implanted into the mammary fat pad are used to model the steps of metastasis. Only 4T1 forms macroscopic lung and liver metastases. Because some miRNAs are dysregulated in cancer and affect cellular transformation, tumor formation, and metastasis, we examined whether changes in miRNA expression might explain the differences in metastasis of these cells.
Methodology/Principal Findings:
miRNA expression was analyzed by miRNA microarray and quantitative RT-PCR in isogenic mouse breast cancer cells with distinct metastatic capabilities. 4T1 cells that form macroscopic metastases had elevated expression of miR-200 family miRNAs compared to related cells that invade distant tissues, but are unable to colonize. Moreover, over-expressing miR-200 in 4TO7 cells enabled them to metastasize to lung and liver. These findings are surprising since the miR-200 family was previously shown to promote epithelial characteristics by inhibiting the transcriptional repressor Zeb2 and thereby enhancing E-cadherin expression. We confirmed these findings in these cells. The most metastatic 4T1 cells acquired epithelial properties (high expression of E-cadherin and cytokeratin-18) compared to the less metastatic cells.
Conclusions/Significance:
Expression of miR-200, which promotes a mesenchymal to epithelial cell transition (MET) by inhibiting Zeb2 expression, unexpectedly enhances macroscopic metastases in mouse breast cancer cell lines. These results suggest that for some tumors, tumor colonization at metastatic sites might be enhanced by MET. Therefore the epithelial nature of a tumor does not predict metastatic outcome.
Insights
MicroRNAs (miRNAs) unexpectedly promote macroscopic metastasis in breast cancer. The miR-200 family enhances tumor colonization by promoting a mesenchymal to epithelial transition (MET), challenging the notion that epithelial traits hinder metastasis.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Metastasis Research
Background:
- Metastasis involves tumor cell dissociation, invasion, and colonization of distant sites, with the latter stage poorly understood.
- Four isogenic mouse breast cancer cell lines (67NR, 168FARN, 4TO7, 4T1) model metastasis, with only 4T1 forming macroscopic lung and liver metastases.
- Dysregulated microRNAs (miRNAs) are implicated in cancer progression and metastasis, prompting investigation into their role in differential metastatic capabilities.
Purpose of the Study:
- To investigate whether altered miRNA expression explains the varying metastatic potential of isogenic mouse breast cancer cell lines.
- To determine the specific role of miR-200 family miRNAs in the colonization and macroscopic metastasis of breast cancer cells.
Main Methods:
- Analysis of miRNA expression using miRNA microarray and quantitative RT-PCR in four distinct mouse breast cancer cell lines.
- Functional studies involving the overexpression of miR-200 in 4TO7 cells to assess its impact on metastatic capability.
- Confirmation of miR-200's effect on epithelial characteristics by measuring E-cadherin and cytokeratin-18 expression.
Main Results:
- 4T1 cells, which form macroscopic metastases, exhibited elevated expression of miR-200 family miRNAs compared to less metastatic cell lines.
- Overexpression of miR-200 in 4TO7 cells significantly enhanced their ability to form lung and liver metastases.
- miR-200 promoted a mesenchymal to epithelial transition (MET) by inhibiting Zeb2, leading to increased E-cadherin expression, consistent with acquired epithelial properties in highly metastatic cells.
Conclusions:
- Contrary to previous findings, miR-200 expression unexpectedly enhances macroscopic metastasis in mouse breast cancer models.
- Mesenchymal to epithelial transition (MET), induced by miR-200, may promote tumor colonization at distant metastatic sites.
- The epithelial nature of a tumor does not reliably predict its metastatic outcome, highlighting a complex role for MET in cancer progression.
