Gambogic acid induces apoptosis by regulating the expression of Bax and Bcl-2 and enhancing caspase-3 activity in human malignant melanoma A375 cells

Int J Dermatol. 2009 Feb;48(2):186-92. doi: 10.1111/j.1365-4632.2009.03946.x.


Objectives: To investigate the effect of a Chinese traditional medicine, gambogic acid (GA), on human malignant melanoma (MM) A375 cells and to study the mechanism of apoptosis induced by GA.

Methods: A375 cells were treated with GA at different doses and for different times, and their proliferation and viability were detected by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis induced by GA in A375 cells was observed by annexin-V/propidium iodide doubling staining flow cytometry assay and Hoechst staining. To further determine the molecular mechanism of apoptosis induced by GA, the changes in expression of Bcl-2 and Bax were detected by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot, and caspase-3 activity was measured by fluorescence resonance energy transfer (FRET) probe.

Results: After incubation with GA, A375 cell proliferation was dramatically inhibited in a dose-dependent manner. After these cells had been exposed to GA for 24, 36 and 48 h, the IC(50) values were 1.57 +/- 0.05, 1.31 +/- 0.20, and 1.12 +/- 0.19 microg/mL, respectively. Treatment of A375 cells with GA (2.5-7.5 microg/mL) for 36 h resulted in an increased number of early apoptotic cells, which ranged from 27.6% to 41.9%, in a dose-dependent manner, compared with only 3.5% apoptotic cells in the non-GA-treated group. An increase in Bax and decrease in Bcl-2 expression were found by real-time RT-PCR and Western blot. Caspase-3 activity was increased in a dose-dependent manner, observed by FRET probe.

Conclusion: GA can inhibit the proliferation of A375 cells and induce their apoptosis, which may be related to the up-regulation of the Bax/Bcl-2 ratio and caspase-3 activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Caspase 3 / metabolism*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Dose-Response Relationship, Drug
  • Fluorescence Resonance Energy Transfer
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Melanoma / drug therapy*
  • Melanoma / pathology
  • Melanoma / physiopathology
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Messenger / metabolism
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / pathology
  • Skin Neoplasms / physiopathology
  • Xanthones / pharmacology*
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism


  • BAX protein, human
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • Xanthones
  • bcl-2-Associated X Protein
  • gambogic acid
  • Caspase 3