Quantitative proteomics reveals ER-α involvement in CD146-induced epithelial-mesenchymal transition in breast cancer cells.

The cell adhesion molecule CD146 is a novel inducer of epithelial-mesenchymal transition (EMT), which was associated with triple-negative breast cancer (TNBC). To gain insights into the complex networks that mediate CD146-induced EMT in breast cancers, we conducted a triple Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC), to analyze whole cell protein profiles of MCF-7 cells that had undergone gradual EMT upon CD146 expression from moderate to high levels. In this study, we identified 2293 proteins in total, of which 103 exhibited changes in protein abundance that correlated with CD146 expression levels, revealing extensive morphological and biochemical changes associated with EMT. Ingenuity Pathway Analysis (IPA) showed that estrogen receptor (ER) was the most significantly inhibited transcription regulator during CD146-induced EMT. Functional assays further revealed that ER-α expression was repressed in cells undergoing CD146-induced EMT, whereas re-expression of ER-α abolished their migratory and invasive behavior. Lastly, we found that ER-α mediated its effects on CD146-induced EMT via repression of the key EMT transcriptional factor Slug. Our study revealed the molecular details of the complex signaling networks during CD146-induced EMT, and provided important clues for future exploration of the mechanisms underlying the association between CD146 and TNBC as observed in the clinic. BIOLOGICAL SIGNIFICANCE: This study used a proteomics screen to reveal molecular changes mediated by CD146-induced epithelial-mesenchymal transition (EMT) in breast cancer cells. Estrogen receptor (ER) was found to be the most significantly inhibited transcription regulator, which mediated its effects on CD146-induced EMT via repression of the transcriptional factor Slug. Elucidation of protein interaction networks and signal networks generated from 103 significantly changed proteins would facilitate future investigation into the mechanisms underlying CD146 induced-EMT in breast cancers.