TY - JOUR
T1 - CD95-mediated apoptosis is impaired at receptor level by cellular FLICE-inhibitory protein (long form) in wild-type p53 human ovarian carcinoma
AU - Mezzanzanica, Delia
AU - Balladore, Emanuela
AU - Turatti, Fabio
AU - Luison, Elena
AU - Alberti, Paola
AU - Bagnoli, Marina
AU - Figini, Mariangela
AU - Mazzoni, Alessandra
AU - Raspagliesi, Francesco
AU - Oggionni, Maria
AU - Pilotti, Silvana
AU - Canevari, Silvana
PY - 2004/8/1
Y1 - 2004/8/1
N2 - Purpose: Ovarian carcinoma is a highly lethal malignancy that often becomes resistant to chemotherapy. Alterations in apoptotic signals and p53 status contribute to drug resistance, and CD95-mediated apoptosis is also deficient in resistant cells. We analyzed the mechanism of resistance to CD95-mediated apoptosis in ovarian carcinoma cell lines differing in p53 status. Experimental Design: CD95-mediated apoptosis was induced by agonistic anti-CD95 antibody, and the apoptotic cascade was monitored with biochemical and functional assays. Results: CD95-mediated apoptosis was blocked in human ovarian cancer cells. In cell lines with wild-type p53, treatment with the protein synthesis inhibitor cycloheximide (CHX) together with anti-CD95 overcame the resistance, suggesting the presence of a labile inhibiting protein. Indeed, the labile protein cellular FLICE-inhibitory protein long form (c-FLIPL) was found to block caspase-8 recruitment to the death-inducing signaling complex (DISC), and sensitization of cells by CHX was due to c-FLIPL down-modulation at the DISC level. Down-regulation of c-FLIPL with antisense oligonucleotides increased CD95-mediated apoptosis as in cells sensitized by CHX, demonstrating the direct involvement of c-FLIPL in apoptosis resistance. Removal of c-FLIPL block at DISC level allowed full activation of the mhochondrial pathway and, eventually, apoptosis in wild-type p53 cells, whereas in cells with mutated p53, c-FLIPL involvement in CD95-mediated apoptosis resistance appeared to be irrelevant. Immunohistochemical analysis of an ovarian tumor tissue array revealed c-FLIPL expression in samples with no p53 accumulation (P = 0.034), and a significant (P = 0.037) inverse relationship between c-FLIPL and p53 expression levels was also observed in 27 epithelial ovarian cancer specimens with known p53 status. Conclusion: The inhibitory protein c-FLIP L is involved in resistance to CD95-mediated apoptosis in ovarian carcinoma cells with wild-type p53.
AB - Purpose: Ovarian carcinoma is a highly lethal malignancy that often becomes resistant to chemotherapy. Alterations in apoptotic signals and p53 status contribute to drug resistance, and CD95-mediated apoptosis is also deficient in resistant cells. We analyzed the mechanism of resistance to CD95-mediated apoptosis in ovarian carcinoma cell lines differing in p53 status. Experimental Design: CD95-mediated apoptosis was induced by agonistic anti-CD95 antibody, and the apoptotic cascade was monitored with biochemical and functional assays. Results: CD95-mediated apoptosis was blocked in human ovarian cancer cells. In cell lines with wild-type p53, treatment with the protein synthesis inhibitor cycloheximide (CHX) together with anti-CD95 overcame the resistance, suggesting the presence of a labile inhibiting protein. Indeed, the labile protein cellular FLICE-inhibitory protein long form (c-FLIPL) was found to block caspase-8 recruitment to the death-inducing signaling complex (DISC), and sensitization of cells by CHX was due to c-FLIPL down-modulation at the DISC level. Down-regulation of c-FLIPL with antisense oligonucleotides increased CD95-mediated apoptosis as in cells sensitized by CHX, demonstrating the direct involvement of c-FLIPL in apoptosis resistance. Removal of c-FLIPL block at DISC level allowed full activation of the mhochondrial pathway and, eventually, apoptosis in wild-type p53 cells, whereas in cells with mutated p53, c-FLIPL involvement in CD95-mediated apoptosis resistance appeared to be irrelevant. Immunohistochemical analysis of an ovarian tumor tissue array revealed c-FLIPL expression in samples with no p53 accumulation (P = 0.034), and a significant (P = 0.037) inverse relationship between c-FLIPL and p53 expression levels was also observed in 27 epithelial ovarian cancer specimens with known p53 status. Conclusion: The inhibitory protein c-FLIP L is involved in resistance to CD95-mediated apoptosis in ovarian carcinoma cells with wild-type p53.
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U2 - 10.1158/1078-0432.CCR-03-0537
DO - 10.1158/1078-0432.CCR-03-0537
M3 - Article
C2 - 15297424
AN - SCOPUS:4143049125
VL - 10
SP - 5202
EP - 5214
JO - Clinical Cancer Research
JF - Clinical Cancer Research
SN - 1078-0432
IS - 15
ER -