Apoptosis induced by Ginkgo biloba (EGb761) in melanoma cells is Mcl-1-dependent

PLoS One. 2015 Apr 10;10(4):e0124812. doi: 10.1371/journal.pone.0124812. eCollection 2015.

Abstract

Melanoma is an aggressive skin cancer. Unfortunately, there is currently no chemotherapeutic agent available to significantly prolong the survival of the most patients with metastatic melanomas. Here we report that the Ginkgo biloba extract (EGb761), one of the most widely sold herbal supplements in the world, potently induces apoptosis in human melanoma cells by disturbing the balance between pro- and anti-apoptosis Bcl-2 family proteins. Treatment with EGb761 induced varying degrees of apoptosis in melanoma cell lines but not in melanocytes. Induction of apoptosis was caspase-dependent and appeared to be mediated by the mitochondrial pathway, in that it was associated with reduction in mitochondrial membrane potential and activation of Bax and Bak. Although EGb761 did not cause significant change in the expression levels of the BH3-only Bcl-2 family proteins Bim, Puma, Noxa, and Bad, it significantly downregulated Mcl-1 in sensitive but not resistant melanoma cells, suggesting a major role of Mcl-1 in regulating apoptosis of melanoma cells induced by EGb761. Indeed, siRNA knockdown of Mcl-1 enhanced EGb761-induced apoptosis, which was associated with increased activation of Bax and Bak. Taken together, these results demonstrate that EGb761 kills melanoma cells through the mitochondrial apoptotic pathway, and that Mcl-1 is a major regulator of sensitivity of melanoma cells to apoptosis induced by EGb761. Therefore, EGb761 with or without in combination with targeting Mcl-1 may be a useful strategy in the treatment of melanoma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Apoptosis / drug effects
  • Caspases / metabolism
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm
  • Gene Knockdown Techniques
  • Ginkgo biloba*
  • Humans
  • Melanoma / drug therapy*
  • Melanoma / metabolism
  • Melanoma / pathology
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Myeloid Cell Leukemia Sequence 1 Protein / antagonists & inhibitors
  • Myeloid Cell Leukemia Sequence 1 Protein / genetics
  • Myeloid Cell Leukemia Sequence 1 Protein / metabolism*
  • Plant Extracts / pharmacology*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Small Interfering / genetics
  • bcl-2 Homologous Antagonist-Killer Protein / metabolism
  • bcl-2-Associated X Protein / metabolism

Substances

  • Antineoplastic Agents, Phytogenic
  • BAK1 protein, human
  • BAX protein, human
  • MCL1 protein, human
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Plant Extracts
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Small Interfering
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • Ginkgo biloba extract
  • Caspases

Grants and funding

This work was supported by research grants from the National Nature Science Foundation (81201560 and 81471551); the priming scientific research foundation for the junior teachers of medicine in Sichuan University (2012SCU11020).