Triptolide's impact on ACER1 signaling: Inducing autophagy for triple-negative breast cancer suppression

Abstract

Given the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (Her-2) in triple-negative breast cancer (TNBC) cells, the efficacy of targeted therapies is limited. In this study, we uncovered that triptolide (TP) effectively suppresses the migration and invasiveness of MDA-MB-231 cells by activating autophagic pathways. Western blotting analysis revealed that TP significantly reduced the expression levels of p62 protein, while simultaneously markedly increasing the expression levels of LC3B-II, BNIP3, BNIP3L, ATG5, and ULK1 proteins, strongly suggesting an enhancement of autophagic activity in the cells. Based on PCR array screening, we identified the ACER1 gene as exhibiting notable expression alterations post-TP treatment. Overexpression of ACER1 gene enhanced the TP-induced apoptosis in MDA-MB-231 cells and augmented the regulation of autophagy-related proteins p62 and LC3B-II, leading to an increase in autophagosome numbers and a marked reduction in cellular migration and invasiveness. Conversely, ACER1 gene knockdown reversed these effects. In vivo experiments demonstrated that TP effectively inhibits the growth of MDA-MB-231 xenograft tumors, concurrently upregulating ACER1 and LC3B-II expression in tumor tissues, while p62 protein levels were notably decreased. Hematoxylin and eosin (H&E) staining results indicated no evident toxicity in liver and kidney tissues of BALB/c mice at a TP dose of 0.4 mg/kg. This study, for the first time, elucidates a novel mechanism by which TP inhibits TNBC through an autophagic process mediated by ACER1.