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p53-dependent Fas expression is critical for Ginsenoside Rh2 triggered caspase-8 activation in HeLa cells
Xiao-Xi Guo1, Yang Li, Chao Sun
1Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, College of Life Science, Jilin University, Changchun, 130012, China.
Abstract:
We have recently reported that Ginsenoside Rh2 (G-Rh2) induces the activation of two initiator caspases, caspase-8 and caspase-9 in human cancer cells. However, the molecular mechanism of its death-inducing function remains unclear. Here we show that G-Rh2 stimulated the activation of both caspase-8 and caspase-9 simultaneously in HeLa cells. Under G-Rh2 treatment, membrane death receptors Fas and TNFR1 are remarkably upregulated. However, the induced expression of Fas but not TNFR1 was contributed to the apoptosis process. Moreover, significant increases in Fas expression and caspase-8 activity temporally coincided with an increase in p53 expression in p53-non-mutated HeLa and SK-HEP-1 cells upon G-Rh2 treatment. In contrast, Fas expression and caspase-8 activity remained constant with G-Rh2 treatment in p53-mutated SW480 and PC-3 cells. In addition, siRNA-mediated knockdown of p53 diminished G-Rh2-induced Fas expression and caspase-8 activation. These results indicated that G-Rh2-triggered extrinsic apoptosis relies on p53-mediated Fas over-expression. In the intrinsic apoptotic pathway, G-Rh2 induced strong and immediate translocation of cytosolic BAK and BAX to the mitochondria, mitochondrial cytochrome c release, and subsequent caspase-9 activation both in HeLa and in SW480 cells. p53-mediated Fas expression and subsequent downstream caspase-8 activation as well as p53-independent caspase-9 activation all contribute to the activation of the downstream effector caspase-3/-7, leading to tumor cell death. Taken together, we suggest that G-Rh2 induces cancer cell apoptosis in a multi-path manner and is therefore a promising candidate for anti-tumor drug development.
Insights
Ginsenoside Rh2 (G-Rh2) triggers cancer cell death through both extrinsic and intrinsic apoptosis pathways. This natural compound activates caspase-8 via p53-dependent Fas upregulation and caspase-9 independently, making it a promising anti-tumor drug candidate.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Ginsenoside Rh2 (G-Rh2) is known to induce apoptosis in human cancer cells.
- The precise molecular mechanisms underlying G-Rh2's cell death-inducing functions require further elucidation.
Purpose of the Study:
- To investigate the molecular mechanisms of Ginsenoside Rh2 (G-Rh2)-induced apoptosis in human cancer cells.
- To determine the roles of p53, Fas, and TNFR1 in G-Rh2-mediated apoptosis.
- To elucidate the involvement of both extrinsic and intrinsic apoptotic pathways in G-Rh2's anti-cancer effects.
Main Methods:
- Treatment of human cancer cell lines (HeLa, SK-HEP-1, SW480, PC-3) with G-Rh2.
- Analysis of caspase-8, caspase-9, and caspase-3/-7 activation.
- Assessment of membrane death receptor (Fas, TNFR1) expression.
- Investigation of p53 expression and its role using siRNA-mediated knockdown.
- Mitochondrial translocation of BAK and BAX, and cytochrome c release assays.
Main Results:
- G-Rh2 simultaneously activated caspase-8 and caspase-9 in HeLa cells.
- G-Rh2 upregulated Fas and TNFR1, with Fas upregulation being crucial for apoptosis.
- p53-dependent Fas upregulation and caspase-8 activation were observed in p53-non-mutated cells, but not in p53-mutated cells.
- G-Rh2 induced intrinsic apoptosis via BAK/BAX translocation, cytochrome c release, and caspase-9 activation, independent of p53 status.
- Both extrinsic and intrinsic pathways converged to activate effector caspases (caspase-3/-7), leading to tumor cell death.
Conclusions:
- Ginsenoside Rh2 (G-Rh2) induces cancer cell apoptosis through a multi-path mechanism involving both extrinsic and intrinsic pathways.
- p53-mediated Fas upregulation is critical for G-Rh2-triggered extrinsic apoptosis.
- G-Rh2's ability to activate multiple apoptotic pathways makes it a promising candidate for anti-tumor drug development.
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