Autophagy induction enhances tetrandrine-induced apoptosis via the AMPK/mTOR pathway in human bladder cancer cells.

Abstract

Tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the roots of Stephania tetrandra is a traditional Chinese medicine and exerts anticancer capacity in various types of cancers. Previous studies have shown that tetrandrine induces apoptosis in bladder cancer cells via activation of the caspase cascade. However, the underlying mechanism has not yet been reported. Autophagy is a cellular process involved in the degradation of broken proteins and aging organelles to maintain homeostasis. Recent studies indicate that autophagy is implicated in cancer therapy. Thus, we focused on the correlation between autophagy and apoptosis upon tetrandrine treatment in human bladder cancer cells. Firstly, our results observed a marked increase in autophagic double-membrane vacuoles and fluorescent puncta of red fluorescence protein-green fluorescence protein-LC3 (GRP-RFP-LC3) upon tetrandrine treatment, as evidenced by transmission electron microscopy and confocal fluorescence microscopy. Secondly, the expression of LC3-II was increased in tetrandrine-treated T24 and 5637 cells in a time- and concentration-dependent manner. Subsequently, downregulation of p62 and LC3 turnover assay further confirmed that tetrandrine induced autophagic flux in bladder cancer T24 and 5637 cells. Thirdly, the protein levels of phosphorylated-AMP-activated protein kinase (AMPK) and phosphorylated-acetyl-coenzyme A carboxylase (ACC) were upregulated in the tetrandrine-treated cells, while the mammalian target of rapamycin (mTOR)-related proteins were downregulated. Moreover, AICAR, a common AMPK activator, further increased the expression the LC3-II, while AMPK inhibitor compound C partially reversed the LC3-II protein levels in bladder cancer T24 cells. Finally, AICAR significantly reinforced the growth inhibition and apoptosis induction of tetrandrine in T24 and 5637 cells, while compound C had an opposite effect, suggesting that AMPK-mediated autophagy enhanced the cytotoxic and pro-apoptosis effect of tetrandrine in human bladder cancer cells. Taken together, the present study showed that tetrandrine induced autophagy in human bladder cancer cells by regulating the AMPK/mTOR signaling pathway, which contributed to the apoptosis induction by tetrandrine, indicating that tetrandrine may be a potential anticancer candidate for the treatment of bladder cancer, and autophagy may be a possible mechanism for cancer therapy.

• Authors: Bo Kou, Wei Liu, Xu Xu, Yang Yang, Qiuyue Yi, Fengwei Guo, Jianpeng Li, Jinsong Zhou, Qingshan Kou
• Journal: Oncology reports (Oncol Rep) Vol. 38 Issue 5 Pg. 3137-3143 (Nov 2017) ISSN: 1791-2431 [Electronic] Greece
• PMID: 29048631 (Publication Type: Journal Article)

Chemical References

• Benzylisoquinolines
• MAP1LC3A protein, human
• Microtubule-Associated Proteins
• Ribonucleotides
• tetrandrine
• Aminoimidazole Carboxamide
• Protein Kinases
• MTOR protein, human
• TOR Serine-Threonine Kinases
• AMP-Activated Protein Kinase Kinases
• AICA ribonucleotide

Topics

• AMP-Activated Protein Kinase Kinases
• Aminoimidazole Carboxamide (administration & dosage, analogs & derivatives)
• Apoptosis (drug effects)
• Autophagy (drug effects, genetics)
• Benzylisoquinolines (administration & dosage)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Drug Resistance, Neoplasm (genetics)
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Microtubule-Associated Proteins (genetics)
• Protein Kinases (drug effects, genetics)
• Ribonucleotides (administration & dosage)
• Signal Transduction (drug effects)
• TOR Serine-Threonine Kinases (genetics)
• Urinary Bladder Neoplasms (drug therapy, genetics, pathology)