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Cisplatin (CDDP) sensitizes human osteosarcoma cell to Fas/CD95-mediated apoptosis by down-regulating FLIP-L
H Kinoshita1, H Yoshikawa, K Shiiki
1Department of Orthopeadic Surgery, Yamanashi Medical University, Yamanashi, Japan.
Abstract:
The mechanisms of escape from Fas/CD95-mediated apoptosis induced by immunosurveillance(NK cells and T cells) in tumor cells are correlated to tumorigenicity. Human osteosarcoma cell MG-63 constitutively expressed cell surface Fas antigen but was resistant to apoptosis by Fas stimulation. However, suboptimal dose of cisplatin(CDDP) could sensitize MG-63 cells to Fas-mediated apoptosis without up-regulation of cell-surface Fas antigen. Western blotting analysis showed that MG-63 cells constitutively expressed FLICE inhibitory protein long form(FLIP-L), which was a novel anti-apoptotic protein and had a potency of tumorigenicity. CDDP down-regulated FLIP-L in a time-dependent manner in MG-63 cells but did not influence expression of other anti-apoptotic molecules such as XIAP, c-IAP-1, c-IAP-2, FADD or pro-caspase-8. Moreover, antisense oligonucleotide to FLIP-L confirmed that down-regulation of FLIP-L induced sensitization to Fas-mediated apoptosis. These findings suggest that FLIP-L contributes to resistance to Fas-mediated apoptosis in MG-63 cells, and sensitization to Fas-mediated apoptosis by CDDP can be a new application of immune therapy.
Insights
Human osteosarcoma cells resist Fas-mediated apoptosis due to FLICE inhibitory protein long form (FLIP-L). Cisplatin (CDDP) sensitizes these cells by down-regulating FLIP-L, suggesting a new immune therapy approach.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Tumor cells can evade immune surveillance, specifically Fas/CD95-mediated apoptosis initiated by NK cells and T cells.
- Human osteosarcoma MG-63 cells express Fas but are resistant to Fas-induced apoptosis.
- Mechanisms of apoptosis resistance are linked to tumorigenicity.
Purpose of the Study:
- To investigate the mechanisms of resistance to Fas-mediated apoptosis in human osteosarcoma MG-63 cells.
- To determine the role of FLICE inhibitory protein long form (FLIP-L) in this resistance.
- To explore the potential of cisplatin (CDDP) in sensitizing these cells to Fas-mediated apoptosis for therapeutic applications.
Main Methods:
- Western blotting to analyze protein expression (FLIP-L, XIAP, c-IAP-1, c-IAP-2, FADD, pro-caspase-8).
- Treatment of MG-63 cells with suboptimal doses of cisplatin (CDDP).
- Antisense oligonucleotide targeting FLIP-L to confirm its role.
Main Results:
- MG-63 cells constitutively express FLIP-L, an anti-apoptotic protein associated with tumorigenicity.
- CDDP treatment down-regulated FLIP-L in a time-dependent manner without affecting other tested anti-apoptotic molecules.
- Down-regulation of FLIP-L using antisense oligonucleotides sensitized MG-63 cells to Fas-mediated apoptosis.
Conclusions:
- FLIP-L is a key contributor to Fas-mediated apoptosis resistance in osteosarcoma MG-63 cells.
- CDDP sensitizes these cells to Fas-mediated apoptosis by down-regulating FLIP-L.
- This sensitization offers a potential new strategy for osteosarcoma immune therapy.
