Histone deacetylase inhibitor downregulation of bcl-xl gene expression leads to apoptotic cell death in mesothelioma.
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.
Cao
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Department of Thoracic and Cardiovascular Surgery, Section of Thoracic Molecular Oncology, the University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Mohuiddin
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Ece
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McConkey
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DJ
Smythe
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WR
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002087:Butyrates / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D020287:In Situ Nick-End Labeling; D008562:Membrane Glycoproteins / Q000378:metabolism; D008654:Mesothelioma; D010997:Pleural Neoplasms; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism
C494811:BCL2L1 protein, human; D002087:Butyrates; D004791:Enzyme Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D056572:Histone Deacetylase Inhibitors; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051020:bcl-X Protein; D019014:fas Receptor; D020169:Caspases; D006655:Histone Deacetylases