FLIP is frequently expressed in endometrial carcinoma and has a role in resistance to TRAIL-induced apoptosis.
The FLICE-inhibitory protein (FLIP) plays a key role in the regulation of apoptosis triggered by death ligands. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in some types of tumor but not in others. To assess the possible role of FLIP in apoptosis resistance in endometrial carcinoma, we performed an immunohistochemical study on a tissue microarray composed of 95 endometrial carcinomas. We found positive signals in 43% of the cases, as well as a significant difference in FLIP expression between stage I and II tumors. Moreover, we observed that endometrial carcinoma cell lines Ishikawa and KLE did not undergo apoptosis after TRAIL treatment. Cotreatment of these cells with the inhibitor of transcription actinomycin D resulted in a dramatic decrease in cell viability and induced activation of caspase-8. These events coincided with downregulation of FLIP mRNA and protein. Inhibitors of caspase-8 or overexpression of FLIP completely blocked apoptosis induced by actinomycin D plus TRAIL cotreatment. More importantly, downregulation of endogenous FLIP expression by specific siRNAs sensitized endometrial carcinoma cells to TRAIL-induced apoptosis in the absence of actinomycin D. Taken together, our results suggest for the first time a critical role for FLIP in the regulation apoptosis triggered by TRAIL in endometrial carcinoma cells.
Dolcet
Xavier
X
Department of Pathology and Molecular Genetics, Hospital Universitari Arnau de Vilanova, University of Lleida, 25198 Lleida, Spain.
Llobet
David
D
Pallares
Judit
J
Rue
Montserrat
M
Comella
Joan X
JX
Matias-Guiu
Xavier
X
D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D045744:Cell Line, Tumor; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D004338:Drug Combinations; D016889:Endometrial Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D040081:Protein Array Analysis; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D004338:Drug Combinations; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin