Histone deacetylase inhibitor downregulation of bcl-xl gene expression leads to apoptotic cell death in mesothelioma

Am J Respir Cell Mol Biol. 2001 Nov;25(5):562-8. doi: 10.1165/ajrcmb.25.5.4539.


It has been shown that mesothelioma expresses the antiapoptotic protein BCL-XL, but not BCL-2, rendering bcl-xl gene expression a potential therapeutic target. Sodium butyrate (NaB) is a histone deacetylase inhibitor capable of alteration of bcl-2 family protein expression in other tumor types. Mesothelioma cell lines (REN, I-45) were exposed to NaB, and viability (colorimetric assay) and apoptosis (TUNEL, Hoescht staining, flow cytometry) were evaluated. Effects on bcl-2 family protein, fas-fas ligand, and caspases were examined by Western blot analysis and functional assay. An RNase assay evaluated bcl-2 family messenger RNA (mRNA) expression. Overexpressing BCL-XL mesothelioma clones were created by plasmid transfer. Cells were sensitive to NaB at low IC(50) (REN, 0.3 mM; I-45, 1 mM) and demonstrated apoptosis (percentage of cells below G1 phase by flow cytometry [sub-G1]: REN, 38.5%; I-45, 30.9%). A significant decrease in BCL-XL protein expression was noted with BAK, BAX, and BCL-2 unchanged, and this was corroborated at the transcriptional level with selectively decreased bcl-xl mRNA production after sodium butyrate exposure. Fas expression and fas-fas ligand sensitivity were unchanged. Caspases demonstrated low-level activation. Stable overexpressing BCL-XL clones were proportionally resistant to the NaB effect. This study suggests that mesothelioma cells are sensitive to the induction of apoptosis related to the attenuation of antiapoptotic bcl-xl gene and protein expression. Additional study of the therapeutic benefit of targeting bcl-xl gene expression in mesothelioma is warranted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Butyrates / pharmacology
  • Caspases / metabolism
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology
  • Dose-Response Relationship, Drug
  • Down-Regulation / drug effects
  • Down-Regulation / physiology
  • Enzyme Inhibitors / pharmacology
  • Fas Ligand Protein
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Expression Regulation, Neoplastic / physiology
  • Histone Deacetylase Inhibitors*
  • Histone Deacetylases / metabolism
  • Humans
  • In Situ Nick-End Labeling
  • Membrane Glycoproteins / metabolism
  • Mesothelioma*
  • Pleural Neoplasms*
  • Proto-Oncogene Proteins c-bcl-2 / genetics*
  • RNA, Messenger / metabolism
  • Tumor Cells, Cultured
  • bcl-X Protein
  • fas Receptor / metabolism


  • BCL2L1 protein, human
  • Butyrates
  • Enzyme Inhibitors
  • FASLG protein, human
  • Fas Ligand Protein
  • Histone Deacetylase Inhibitors
  • Membrane Glycoproteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • bcl-X Protein
  • fas Receptor
  • Caspases
  • Histone Deacetylases