Acid ground nano‐realgar processed product inhibits breast cancer by inducing mitophagy via the p53/BNIP3/NIX pathway

Abstract Breast cancer is a highly prevalent malignancy with the first morbidity and the primary reason for female cancer‐related deaths worldwide. Acid ground nano‐realgar processed product (NRPP) could inhibit breast cancer cell proliferation and induce autophagy in our previous research; however, the underlying mechanisms are still unclear. Therefore, this research aimed to verify whether NRPP induces breast cancer mitophagy and explore the mitophagy‐mediated mechanism. Primarily, rhodamine‐123 assay and transmission electron microscopy were applied to detect mitochondrial membrane potential (MMP) and ultrastructural changes in the MDA‐MB‐435S cells, respectively. Mito‐Tracker Green/Lyso‐Tracker Red staining, western blot, immunofluorescence and RT‐PCR were used to explore molecular mechanisms of NRPP‐induced mitophagy in vitro. MDA‐MB‐435S breast cancer xenograft models were established to assess the activity and mechanisms of NRPP in vivo. Our results showed that NRPP decreased MMP and increased autophagosome numbers in MDA‐MB‐435S cells and activated mitophagy. Furthermore, mitophagy was consolidated because mitochondria and lysosomes colocalized phenomenology were observed, and the expression of LC3II/I and COXIV was upregulated. Additionally, we found the p53/BNIP3/NIX pathway was activated. Finally, NRPP inhibited tumour growth and downregulated the levels of TNF‐α, IL‐1β and IL‐6. Necrosis, damaged mitochondria and autophagosomes were observed in xenograft tumour cells, and proteins and mRNA levels of LC3, p53, BNIP3 and NIX were increased. Overall, NRPP inhibited MDA‐MB‐435S cell proliferation and tumour growth by inducing mitophagy via the p53/BNIP3/NIX pathway. Thus, NRPP is a promising candidate for breast cancer treatment.