Rosmarinic acid inhibits stem-like breast cancer through hedgehog and Bcl-2/Bax signaling pathways

Background: Rosmarinic acid (RA) is a natural phenolic acid present in various Lamiaceae herbs. RA shows anti-tumor effects on many tumors but has yet to be tested on triple negative breast cancer and its derived breast cancer stem-like cells (BCSCs). Objective: This study aimed to detect whether RA could inhibit the proliferation and migration of BCSCs through hedgehog (Hh) signaling while promoting apoptosis via Bcl-2/Bax. Materials and Methods: BCSCs from the human breast cancer cell line MD-MB-231 were isolated by fluorescence-activated cell sorting with the surface markers of CD44*/CD24-/low. The viability, migration, and apoptosis of BCSCs were assessed by the CCK-8 assay, cell wound healing test, and flow cytometry for positive staining for Annexin V-FITC and propidium iodine (PI), respectively. mRNA and protein levels of Hh and Bcl-2/Bax signaling pathways were obtained by real-time reverse transcriptase polymerase chain reaction and immunoblots. Results: RA inhibited the viability and migration of BCSCs and increased the numbers of late apoptotic cells. Consistent with the increased apoptosis, RA treatment downregulated Bcl-2 while upregulating Bax expression. In line with its effect to limit migration, RA treatment inhibited the expression of Hh-related genes smoothened and glioma-associated oncogene homolog 1. Conclusion: The present study suggests that RA exerts anti-cancer effects on BCSCs by inhibiting Bcl-2 and Hh signaling pathways.