Epithelial membrane protein 2: a novel biomarker for circulating tumor cell recovery in breast cancer
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EpCAM is a common marker used in the detection of circulating tumor cells (CTC). Disseminated cancer cells display the characteristics of epithelial-to-mesenchymal transition events. The purpose of this study was to assess the potential of epithelial membrane protein 2 (EMP2) as a novel biomarker for CTC retrieval in breast cancer.
MCF7 and MDA-MB-231 cells were stained with either anti-EpCAM or anti-EMP2 mAbs, respectively, followed by flow cytometric assay to measure their expression levels. PBMCs isolated from healthy donors were used for breast cancer cell spiking. CD45-depleted PBMCs from breast cancer patients’ blood were used for CTC capturing. Immunomagnetic separation was used to enrich breast cancer cells. Cytospin centrifugation was performed to concentrate the captured cells, followed by immunofluorescence staining with anti-CD45 mAb, anti-pan cytokeratin mAb and DAPI. Fluorescent images were taken using a confocal microscope for CTC counts.
MDA-MB-231 cells had 2.56 times higher EMP2 expression than MCF7 cells, and EMP2 had a significantly higher capture efficiency than EpCAM for MCF7 cells. Furthermore, anti-EMP2 was capable of capturing MCF7 cells that escaped in the flow-through of anti-EpCAM. Likewise, EMP2 had a significantly higher capture efficiency on MDA-MB-231 cells when compared to MCF7 cells. Most importantly, EMP2 biomarker was successfully used for CTC capture in patients with primary breast cancer.
EMP2 is superior to EpCAM for capturing both MCF7 and MDA-MB-231 cells. Additionally, EMP2 is a novel biomarker and capable of capturing breast cancer cells in patient blood samples.
KeywordsEpithelial membrane protein 2 Circulating tumor cells Breast cancer Biomarker Capture
The authors would like to thank Dr. Shengwen Shao at the Institute of Microbiology and Immunology, Huzhou University School of Medicine for his professional help on cell-staining and images taking.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
This study was reviewed and approved by the ethics committee of the institutional review board (IRB, HU2014-04), the First Hospital Affiliated to Huzhou University School of Medicine. All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee.
Informed consent forms were obtained from all individual participants who were included in the study.
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