Breast cancer is a highly heterogeneous disease that has been clinically divided into three main subtypes: estrogen receptor (ER)- and progesterone receptor (PR)-positive, human epidermal growth factor receptor 2 (HER 2)-positive, and triple-negative breast cancer (TNBC). With its high metastatic potential and resistance to endocrine therapy, HER 2-targeted therapy, and chemotherapy, TNBC represents an enormous clinical challenge. The genus Taraxacum is used to treat breast cancer in traditional medicine. Here, we applied aqueous extracts from two Taraxacum species, T. mongolicum and T. formosanum, to compare their potential antitumor effects against three human breast cancer cell lines: MDA-MB-231 (ER-, PR-, and HER2-), ZR-75-1 (ER+, PR+/-, and HER2-), and MCF-7 (ER+, PR+, and HER2-). Our results show that T. mongolicum exerted cytotoxic effects against MDA-MB-231 cells, including the induction of apoptosis, the reduction of cell proliferation, the disruption of the mitochondrial membrane potential, and/or the downregulation of the oxygen consumption rate. Both T. mongolicum and T. formosanum decreased cell migration and colony formation in the three cell-lines and exerted suppressive effects on MCF-7 cell proliferation based on metabolic activity and BrdU incorporation, but an enhanced proliferation of ZR-75-1 cells based on BrdU incorporation. T. formosanum induced ribotoxic stress in MDA-MB-231and ZR-75-1 cells; T. mongolicum did not. In summary, these findings suggest that T. mongolicum showed greater cytotoxicity against all three tested breast cancer cell lines, especially the TNBC MDA-MB-231 cell line.
Keywords: Taraxacum; cytotoxicity; oxygen consumption rate; ribotoxic stress; triple-negative breast cancer.