Cyclovirobuxine D induces autophagy-associated cell death via the Akt/mTOR pathway in MCF-7 human breast cancer cells

J Pharmacol Sci. 2014;125(1):74-82. doi: 10.1254/jphs.14013fp. Epub 2014 Apr 24.

Abstract

Autophagy is a highly regulated and multi-step biological process that serves to remove damaged cytoplasmic components and organelles. It has been suggested that the activation of autophagy may be a promising therapeutic strategy for cancer treatment by triggering cell death. In this study, we reported that cyclovirobuxine D (CVB-D), an alkaloid component in a traditional Chinese herb, could induce autophagy in the MCF-7 human breast cancer cell line. CVB-D inhibited the viability of MCF-7 cells in a concentration- and time-dependent manner. Activation of autophagy was characterized by transmission electron microscopy, monodansylcadaverine staining, and expression of autophagy marker microtubule-associated protein 1 light chain 3 (LC3). After CVB-D treatment, a clear accumulation of autophagosomes was observed accompanied with elevated LC3 fluorescent puncta. Western blot analysis revealed that CVB-D significantly promoted the conversion from LC3-I to LC3-II and the expression of autophagy-related protein 5 (ATG5), which are both essential for autophagosome formation. On the other hand, CVB-D-induced autophagy and decrease in cell viability could be blocked by 3-methyladenine, a well-established autophagy inhibitor. Moreover, CVB-D attenuated the phosphorylation of Akt and mTOR, two pivotal suppressors in autophagy pathways. These findings shed new light on the pharmacological actions and mechanism of CVB-D and may support the potential utility of autophagy inducers in cancer treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Autophagy / drug effects*
  • Autophagy / genetics
  • Autophagy-Related Protein 5
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology*
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • Drugs, Chinese Herbal / chemistry*
  • Drugs, Chinese Herbal / pharmacology
  • Drugs, Chinese Herbal / therapeutic use
  • Female
  • Humans
  • MCF-7 Cells
  • Microtubule-Associated Proteins / metabolism
  • Molecular Targeted Therapy
  • Phosphorylation / drug effects
  • Phytotherapy
  • Proto-Oncogene Proteins c-akt / metabolism
  • Signal Transduction / drug effects*
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • ATG5 protein, human
  • Autophagy-Related Protein 5
  • Drugs, Chinese Herbal
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • 3-methyladenine
  • cyclovirobuxine D
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases
  • Adenine