Daurisoline inhibits proliferation, induces apoptosis, and enhances TRAIL sensitivity of breast cancer cells by upregulating DR5

Abstract Daurisoline (DS) is an isoquinoline alkaloid that exerts anticancer activities in various cancer cells. However, the underlying mechanisms through which DS affects the survival of breast cancer cells remain poorly understood. Therefore, the present study was undertaken to investigate the potential anticancer effect of DS on breast cancer cells and reveal the mechanism underlying the enhanced tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL)‐mediated apoptosis by DS. Cell counting kit‐8 (CCK‐8) and 5‐ethynyl‐2‐deoxyuridine (EdU) assay were used to evaluate the ability of cell proliferation. Flow cytometry was selected to examine the cell cycle distribution. TUNEL assay was used to detect the cell apoptosis. The protein expression was measured by Western blot analysis. DS was found to reduce the cell viability and suppress the proliferation of MCF‐7 and MDA‐MB‐231 cells by causing G1 phase cell cycle arrest. DS could trigger apoptosis by promoting the cleavage of caspase‐8 and PARP. The phosphorylation of ERK, JNK, and p38MAPK was upregulated clearly following DS treatment. Notably, SP600125 (JNK inhibitor) pretreatment significantly abrogated DS‐induced PARP cleavage. DS inactivated Akt/mTOR and Wnt/β‐catenin signaling pathway and upregulated the expression of ER stress‐related proteins. Additionally, DS amplified TRAIL‐caused viability reduction and apoptosis in breast cancer cells. Mechanismly, DS upregulated the protein level of DR4 and DR5, and knockdown of DR5 attenuated the cotreatment‐induced cleavage of PARP. Inhibition of JNK could block DS‐induced upregulation of DR5. This study provides valuable insights into the mechanisms of DS inhibiting cell proliferation, triggering apoptosis, and enhancing TRAIL sensitivity of breast cancer cells.