UVA Irradiation Enhances Brusatol-Mediated Inhibition of Melanoma Growth by Downregulation of the Nrf2-Mediated Antioxidant Response

Oxid Med Cell Longev. 2018 Feb 18:2018:9742154. doi: 10.1155/2018/9742154. eCollection 2018.

Abstract

Brusatol (BR) is a potent inhibitor of Nrf2, a transcription factor that is highly expressed in cancer tissues and confers chemoresistance. UVA-generated reactive oxygen species (ROS) can damage both normal and cancer cells and may be of potential use in phototherapy. In order to provide an alternative method to treat the aggressive melanoma, we sought to investigate whether low-dose UVA with BR is more effective in eliminating melanoma cells than the respective single treatments. We found that BR combined with UVA led to inhibition of A375 melanoma cell proliferation by cell cycle arrest in the G1 phase and triggers cell apoptosis. Furthermore, inhibition of Nrf2 expression attenuated colony formation and tumor development from A375 cells in heterotopic mouse models. In addition, cotreatment of UVA and BR partially suppressed Nrf2 and its downstream target genes such as HO-1 along with the PI3K/AKT pathway. We propose that cotreatment increased ROS-induced cell cycle arrest and cellular apoptosis and inhibits melanoma growth by regulating the AKT-Nrf2 pathway in A375 cells which offers a possible therapeutic intervention strategy for the treatment of human melanoma.

MeSH terms

  • Animals
  • Antioxidants / metabolism*
  • Apoptosis / drug effects
  • Apoptosis / radiation effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Proliferation / radiation effects
  • Dose-Response Relationship, Radiation
  • Down-Regulation* / drug effects
  • Down-Regulation* / radiation effects
  • Gene Knockout Techniques
  • Humans
  • Inactivation, Metabolic / drug effects
  • Inactivation, Metabolic / radiation effects
  • Melanoma / drug therapy*
  • Melanoma / pathology*
  • Mice, Nude
  • NF-E2-Related Factor 2 / genetics*
  • NF-E2-Related Factor 2 / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quassins / pharmacology
  • Quassins / therapeutic use*
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • Ultraviolet Rays*

Substances

  • Antioxidants
  • NF-E2-Related Factor 2
  • Quassins
  • Reactive Oxygen Species
  • brusatol
  • Proto-Oncogene Proteins c-akt