Dexamethasone enhances trichosanthin-induced apoptosis in the HepG2 hepatoma cell line
Meng Li1, Fei Chen, Cui-Ping Liu
1Institute of Cell Biology, Zhejiang University Medical School, Hangzhou 310058, China.
Aims:
Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) with antitumor activities for various cancers. In this paper, we aimed to investigate whether dexamethasone, an important synthetic member of the glucocorticoid steroids, in combination with TCS can be a potential therapy in treating hepatoma.
Main Methods:
Cell viability was investigated using MTT assay, and apoptosis was evaluated with Hoechst 33258 staining. Western blot analysis was used to examine the changes in the expression levels of IkappaB-alpha, NF-kappaB p65 subunit and Cox-2. Additionally, we took advantage of dominant-negative IkappaB (IkappaB-DM) over-expression and chemical inhibitor PDTC to inhibit NF-kappaB activation.
Key Findings:
Our results demonstrated that dexamethasone could enhance TCS-induced apoptosis in the hepatoma cell line HepG2, decreasing IC50 values from in excess of 200microg/ml to 50microg/ml. In addition, our results demonstrated that TCS could induce rapid degradation of IkappaB-alpha, nuclear translocation of NF-kappaB and decrease of COX-2 expression in HepG2 cells. Inhibition of NF-kappaB by biological (IkappaB-DM) or chemical inhibitor (PDTC) increased HepG2 cells' sensitivity to TCS, resulting in cell viability rate decreasing and apoptotic rate increasing. Simultaneously, dexamethasone increased the level of IkappaB-alpha protein and effectively inhibited TCS-induced degradation of IkappaB-alpha.
Significance:
These results suggest that dexamethasone could enhance trichosanthin-induced apoptosis in the HepG2, at least in part, by inhibiting the NF-kappaB signaling pathway and thus strengthening the antitumor effects of TCS, which highlights the possibility of combined drug application of TCS and dexamethasone in the clinical treatment of hepatoma.
Insights
Dexamethasone enhances trichosanthin (TCS)-induced apoptosis in hepatoma cells by inhibiting the NF-kappaB pathway. This combination therapy shows potential for treating liver cancer, strengthening antitumor effects.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Trichosanthin (TCS), a ribosome-inactivating protein (RIP), exhibits antitumor properties against various cancers.
- Hepatoma remains a significant global health challenge, necessitating novel therapeutic strategies.
Purpose of the Study:
- To investigate the synergistic potential of dexamethasone and TCS in treating hepatoma.
- To elucidate the underlying molecular mechanisms, particularly the role of the NF-kappaB signaling pathway.
Main Methods:
- Cell viability assessed via MTT assay; apoptosis evaluated using Hoechst 33258 staining.
- Western blot analysis monitored IkappaB-alpha, NF-kappaB p65, and COX-2 expression.
- NF-kappaB activation inhibited using dominant-negative IkappaB (IkappaB-DM) and PDTC.
Main Results:
- Dexamethasone enhanced TCS-induced apoptosis in HepG2 cells, reducing IC50 from >200 to 50 μg/ml.
- TCS induced IkappaB-alpha degradation and NF-kappaB nuclear translocation, decreasing COX-2 expression.
- Inhibition of NF-kappaB increased HepG2 sensitivity to TCS, boosting apoptosis and reducing viability. Dexamethasone counteracted TCS-induced IkappaB-alpha degradation.
Conclusions:
- Dexamethasone potentiates TCS-induced apoptosis in hepatoma cells, partly via NF-kappaB pathway inhibition.
- The combination of TCS and dexamethasone demonstrates enhanced antitumor effects, suggesting clinical applicability for hepatoma treatment.
