The mechanism of acacetin-induced apoptosis on oral squamous cell carcinoma

Arch Oral Biol. 2015 Sep;60(9):1283-98. doi: 10.1016/j.archoralbio.2015.05.009. Epub 2015 Jun 8.

Abstract

Background: Acacetin (5,7-dihydroxy-40-methoxyflavone), present in safflower seeds, plants, flowers, Cirisium rhinoceros Nakai, has been reported to be able to exert anti-peroxidative, anti-inflammatory, anti-plasmodial, and anti-proliferative activities by inducing apoptosis and blocking the progression of cell cycles.

Objective and design: The objective of this study is to investigate the mechanism of acacetin-induced apoptosis of oral squamous cell carcinoma cell line (HSC-3).

Results: Acacetin caused 50% growth inhibition (IC50) of HSC-3 cells at 25μg/mL over 24h in the MTT assay. Apoptosis was characterized by DNA fragmentation and increase of sub-G1 cells and involved activation of caspase-3 and PARP (poly-ADP-ribose polymerase). Maximum caspase-3 activity was observed with 100μg/mL of acacetin for 24h. Caspase-8 and -9 activation cascades mediated the activation of caspase-3. Acacetin caused reduction of Bcl-2 expression leading to an increase of the Bax:Bcl-2 ratio. It also caused a loss of mitochondrial membrane potential that induced release of cytochrome c into the cytoplasm. Pretreatment with casapse-3 (Z-DEVD-FMK), -8 (Z-IETD-FMK), and 9 inhibitor (z-LEHD-fmk) inhibited the acacetin-induced loss of mitochondrial membrane potential and release of cytochrome c. The mitogen-activated protein kinases (MAPKs) were activated by acacetin. Moreover, pretreating the cells with each of the caspase inhibitor or MAPKs specific inhibitors apparently inhibited acacetin-induced cytotoxicity of HSC-3 cells.

Conclusion: In conclusion, acacetin induce the apoptosis of oral squamous cell carcinoma cell line, which is closely related to its ability to activate the MAPK-mediated signaling pathways with the subsequent induction of a mitochondria- and caspase-dependent mechanism. These results strongly suggest that acacetin might have cancer inhibition and therapeutic potential.

Keywords: Acacetin; Apoptosis; Caspases; Cell cycles; MAPKs signal pathway; Mitochondrial pathway; Oral cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Blotting, Western
  • Carcinoma, Squamous Cell / drug therapy*
  • Carcinoma, Squamous Cell / enzymology
  • Caspase 3 / metabolism
  • Caspase 8 / metabolism
  • Caspase 9 / metabolism
  • Cell Cycle
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cytochromes c / metabolism
  • DNA Fragmentation
  • Flavones / pharmacology*
  • Flow Cytometry
  • Humans
  • In Situ Nick-End Labeling
  • Membrane Potential, Mitochondrial / drug effects
  • Mitogen-Activated Protein Kinases / metabolism
  • Mouth Neoplasms / drug therapy*
  • Mouth Neoplasms / enzymology
  • Oligopeptides / pharmacology
  • Poly(ADP-ribose) Polymerases / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Signal Transduction

Substances

  • Flavones
  • Oligopeptides
  • Proto-Oncogene Proteins c-bcl-2
  • benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone
  • benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone
  • benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone
  • Cytochromes c
  • Poly(ADP-ribose) Polymerases
  • Mitogen-Activated Protein Kinases
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • acacetin