Inhibition of autophagy induced by tetrandrine promotes the accumulation of reactive oxygen species and sensitizes efficacy of tetrandrine in pancreatic cancer

Abstract

Pancreatic cancer, characterized by its poor prognosis, exhibits a marked resistance to conventional chemotherapy and immunotherapy, underscoring the urgent need for more effective treatment modalities. In light of this, the present study is designed to assess the potential antineoplastic efficacy of a combined regimen involving tetrandrine, a plant-derived alkaloid, and autophagy inhibitors in the context of pancreatic cancer. Electron microscopy and immunoblots showed that tetrandrine promoted the formation of autophagosomes and the upregulation of LC3II and the downregulation of p62 expression, indicating that tetrandrine induced autophagy in pancreatic cancer cells. Western blot revealed that tetrandrine inhibited the phosphorylation of AKT and mTOR, as well as the expression of Bcl-2, while upregulating Beclin-1 expression. Moreover, tetrandrine promoted the transcription and protein expression of ATG7. Following the combination of autophagy inhibitors and tetrandrine, the apoptotic rate and cell death significantly increased in pancreatic cancer cells. Consistent results were obtained when ATG7 was silenced. Additionally, tetrandrine induced the generation of ROS, which was involved in the activation of autophagy and apoptosis. Further investigation revealed that upon autophagy inhibition, ROS accumulated in pancreatic cancer cells, resulting in decreased mitochondrial membrane potential and further induction of apoptosis. The results of treating subcutaneous xenograft tumors with a combination of tetrandrine and chloroquine validated that autophagy inhibition enhances the toxicity of tetrandrine against pancreatic cancer in vivo. Altogether, our study demonstrates that tetrandrine induces cytoprotective autophagy in pancreatic cancer cells. Inhibiting tetrandrine-induced autophagy promotes the accumulation of ROS and enhances its toxicity against pancreatic cancer.