Quantitative phosphoproteomic analysis reveals γ-bisabolene inducing p53-mediated apoptosis of human oral squamous cell carcinoma via HDAC2 inhibition and ERK1/2 activation

Proteomics. 2015 Oct;15(19):3296-309. doi: 10.1002/pmic.201400568. Epub 2015 Aug 13.


γ-Bisabolene, one of main components in cardamom, showed potent in vitro and in vivo anti-proliferative activities against human oral squamous cell carcinoma (OSCC). γ-Bisabolene activated caspases-3/9 and decreased mitochondrial memebrane potential, leading to apoptosis of OSCC cell lines (Ca9-22 and SAS), but not normal oral fibroblast cells. Phosphoproteome profiling of OSCC cells treated with γ-bisabolene was identified using TiO2-PDMS plate and LC-MS/MS, then confirmed using Western blotting and real-time RT-PCR assays. Phosphoproteome profiling revealed that γ-bisabolene increased the phosphorylation of ERK1/2, protein phosphatases 1 (PP1), and p53, as well as decreased the phosphorylation of histone deacetylase 2 (HDAC2) in the process of apoptosis induction. Protein-protein interaction network analysis proposed the involvement of PP1-HDAC2-p53 and ERK1/2-p53 pathways in γ-bisabolene-induced apoptosis. Subsequent assays indicated γ-bisabolene eliciting p53 acetylation that enhanced the expression of p53-regulated apoptotic genes. PP1 inhibitor-2 restored the status of HDAC2 phosphorylation, reducing p53 acetylation and PUMA mRNA expression in γ-bisabolene-treated Ca9-22 and SAS cells. Meanwhile, MEK and ERK inhibitors significantly decreased γ-bisabolene-induced PUMA expression in both cancer cell lines. Notably, the results ascertained the involvement of PP1-HDAC2-p53 and ERK1/2-p53 pathways in mitochondria-mediated apoptosis of γ-bisabolene-treated cells. This study demonstrated γ-bisabolene displaying potent anti-proliferative and apoptosis-inducing activities against OSCC in vitro and in vivo, elucidating molecular mechanisms of γ-bisabolene-induced apoptosis. The novel insight could be useful for developing anti-cancer drugs.

Keywords: Cell biology; Histone deacetylase; Oral squamous cell carcinoma; P53 acetylation; Phosphoproteomics; γ-Bisabolene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Carcinoma, Squamous Cell / drug therapy
  • Carcinoma, Squamous Cell / enzymology
  • Carcinoma, Squamous Cell / metabolism*
  • Histone Deacetylase 2 / antagonists & inhibitors*
  • Humans
  • MAP Kinase Signaling System / drug effects*
  • Mice
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mouth Neoplasms / drug therapy
  • Mouth Neoplasms / enzymology
  • Mouth Neoplasms / metabolism*
  • Phosphoproteins / analysis
  • Proteomics
  • Sesquiterpenes / pharmacology*
  • Sesquiterpenes / therapeutic use
  • Tumor Suppressor Protein p53 / metabolism*


  • Phosphoproteins
  • Sesquiterpenes
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • gamma-bisabolene
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • HDAC2 protein, human
  • Histone Deacetylase 2