Triterpene Acid (---Coumaroyltormentic Acid) Isolated From Aronia Extracts Inhibits Breast Cancer Stem Cell Formation through Downregulation of c-Myc Protein.

Cancer stem cells (CSCs) are drug-resistant and radiation-resistant cancer cells that are responsible for tumor progression and maintenance, cancer recurrence, and metastasis. Targeting breast CSCs with phytochemicals is a new paradigm for cancer prevention and treatment. In this study, activity-guided fractionation from mammosphere formation inhibition assays, repeated chromatographic preparations over silica gel, preparatory thin layer chromatography, and HPLC using aronia extracts led to the isolation of one compound. Using ¹H and C 2-dimensional nuclear magnetic resonance (NMR) as well as electrospray ionization (ESI) mass spectrometry, the isolated compound was identified as ---coumaroyltormentic acid. This compound inhibits breast cancer cell proliferation and mammosphere formation in a dose-dependent manner and reduces the CD44/CD24 subpopulation and aldehyde dehydrogenase (ALDH)-expressing cell population as well as the expression of the self-renewal-related genes , , and ---Coumaroyltormentic acid preferentially reduced the protein levels of c-Myc, which is a CSC survival factor, by inducing c-Myc degradation. These findings indicate the novel utilization of ---coumaroyltormentic acid for breast cancer therapy via disruption of c-Myc protein, which is a CSC survival factor.