Silencing of death receptor and caspase-8 expression in small cell lung carcinoma cell lines and tumors by DNA methylation.
Small cell lung cancer cell lines were resistant to FasL and TRAIL-induced apoptosis, which could be explained by an absence of Fas and TRAIL-R1 mRNA expression and a deficiency of surface TRAIL-R2 protein. In addition, caspase-8 expression was absent, whereas FADD, FLIP and caspases-3, -7, -9 and -10 could be detected. Analysis of SCLC tumors revealed reduced levels of Fas, TRAIL-R1 and caspase-8 mRNA compared to non-small cell lung cancer (NSCLC) tumors. Methylation-specific PCR demonstrated methylation of CpG islands of the Fas, TRAIL-R1 and caspase-8 genes in SCLC cell lines and tumor samples, whereas NSCLC samples were not methylated. Cotreatment of SCLC cells with the demethylating agent 5'-aza-2-deoxycytidine and IFNgamma partially restored Fas, TRAIL-R1 and caspase-8 expression and increased sensitivity to FasL and TRAIL-induced death. These results suggest that SCLC cells are highly resistant to apoptosis mediated by death receptors and that this resistance can be reduced by a combination of demethylation and treatment with IFNgamma.
Hopkins-Donaldson
S
S
University Hospital Zürich, Switzerland. Sally.Donaldson@dim.usz.ch
Ziegler
A
A
Kurtz
S
S
Bigosch
C
C
Kandioler
D
D
Ludwig
C
C
Zangemeister-Wittke
U
U
Stahel
R
R
D017209:Apoptosis; D015153:Blotting, Western; D018288:Carcinoma, Small Cell / Q000378:metabolism*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007371:Interferon-gamma / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D019014:fas Receptor / Q000096:biosynthesis*
D018076:DNA, Complementary; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; D019014:fas Receptor; D012313:RNA; D007371:Interferon-gamma; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases