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Updated: Apr 11, 2026
Cytotoxic Efficacy of Photodynamic Therapy in Osteosarcoma Cells In Vitro
Published on: March 18, 2014
Celastrol overcomes 5-fluorouracil resistance in osteosarcoma cells through p53-mediated apoptotic pathway modulation
Mohammad Ebrahimnezhad1,2, Amir Valizadeh1,2, Bahman Yousefi2,3
1Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
Introduction:
Osteosarcoma, a prevalent malignant bone tumor in children and adolescents, is hindered by chemoresistance, particularly to 5-fluorouracil (5-FU), driven by mechanisms such as P-glycoprotein (P-gp) overexpression and altered p53 signaling. Celastrol, a triterpenoid, exhibits anti-tumor properties, but its potential to overcome 5-FU resistance in osteosarcoma remains underexplored.
Methods:
We investigated the synergistic effects of celastrol and 5-FU in human osteosarcoma cell lines with varying p53 statuses (U-2OS, wild-type; SaOS-2, p53-null; HOS, mutant p53) using MTT assays for cytotoxicity, Chou-Talalay method for synergy, and Cell Death Detection ELISA for apoptosis. Gene expression (p53, Bax, Bcl-2, caspase-9) was quantified via qRT-PCR, P-gp levels by Western blot, and P-gp efflux activity by Rhodamine 123 assays. Non-malignant hFOB 1.19 cells served as controls.
Results:
Celastrol and 5-FU exhibited potent cytotoxicity, with combination therapy reducing IC₅₀ values 3.7- to 11.9-fold across cell lines, showing strong synergy. The combination significantly enhanced apoptosis and modulated p53-dependent (U-2OS) and -independent (SaOS-2, HOS) pathways, upregulating Bax and caspase-9 while downregulating Bcl-2. Celastrol reduced P-gp expression and increased intracellular drug accumulation, comparable to verapamil.
Conclusion:
Celastrol synergizes with 5-FU to overcome chemoresistance in osteosarcoma by enhancing p53-mediated and -independent apoptosis and inhibiting P-gp-mediated drug efflux. These findings suggest a promising low-toxicity therapeutic strategy, warranting further in vivo and clinical investigations.
Insights
Celastrol combined with 5-fluorouracil (5-FU) overcomes osteosarcoma chemoresistance by boosting apoptosis and inhibiting drug efflux. This combination therapy shows promise for treating resistant bone cancers.
Area of Science:
- Oncology
- Pharmacology
- Molecular Biology
Background:
- Osteosarcoma is a common childhood bone cancer with limited treatment options due to chemoresistance.
- 5-fluorouracil (5-FU) resistance in osteosarcoma is often linked to P-glycoprotein (P-gp) overexpression and altered p53 signaling.
- Celastrol, a natural compound, has shown anti-tumor effects but its role in overcoming 5-FU resistance in osteosarcoma is not well understood.
Purpose of the Study:
- To investigate the synergistic effects of celastrol and 5-FU on osteosarcoma cell lines.
- To determine if celastrol can overcome 5-FU resistance by affecting apoptosis and P-gp activity.
- To evaluate the role of p53 status in the response to combination therapy.
Main Methods:
- Utilized human osteosarcoma cell lines with varying p53 statuses (wild-type, null, mutant).
- Assessed cytotoxicity and apoptosis using MTT assays and Cell Death Detection ELISA.
- Quantified gene expression, P-gp levels, and P-gp efflux activity to understand underlying mechanisms.
Main Results:
- Celastrol and 5-FU demonstrated significant synergistic cytotoxicity, reducing IC50 values substantially.
- Combination therapy markedly enhanced apoptosis through p53-dependent and -independent pathways.
- Celastrol effectively reduced P-gp expression and activity, increasing intracellular 5-FU accumulation.
Conclusions:
- Celastrol synergizes with 5-FU to overcome osteosarcoma chemoresistance.
- The combination enhances apoptosis and inhibits P-gp-mediated drug efflux.
- This approach presents a potential low-toxicity strategy for treating resistant osteosarcoma, meriting further research.
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