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Cisplatin and taxol activate different signal pathways regulating cellular injury-induced expression of GADD153
D P Gately1, A Sharma, R D Christen
1Department of Biomedical Sciences, University of California, San Diego, La Jolla 92093-0812, USA.
Abstract:
Signal transduction pathways activated by injury play a central role in coordinating the cellular responses that determine whether a cell survives or dies. GADD153 expression increases markedly in response to some types of cellular injury and the product of this gene causes cell cycle arrest. Using induction of GADD153 as a model, we have investigated the activation of the cellular injury response after treatment with taxol and cisplatin (cDDP). Activation of the GADD153 promoter coupled to the luciferase gene and transfected into human ovarian carcinoma 2008 cells correlated well with the increase in endogenous GADD153 mRNA after treatment with taxol but not after treatment with cDDP. Following treatment with cDDP, the increase in endogenous GADD153 mRNA was 10-fold greater than the increase in GADD153 promoter activity. Likewise, at equitoxic levels of exposure (IC80), cDDP produced a 5-fold greater increase in endogenous GADD153 mRNA than taxol. The tyrosine kinase inhibitor tyrophostin B46 had no significant effect on the ability of taxol to activate the GADD153 promoter, but inhibited activation of the GADD153 promoter by cDDP in a concentration-dependent manner. Tyrphostin B46 synergistically enhanced the cytotoxicity of cisplatin; however, the same exposure had no significant effect on the cytotoxicity of taxol. We conclude that (1) taxol and cDDP activate GADD153 promoter activity through different mechanisms; (2) the signal transduction pathway mediating induction by cDDP involves a tyrosine kinase inhibitable by tyrphostin B46; and (3) that inhibition of this signal transduction pathway by tyrphostin synergistically enhances cDDP toxicity.
Insights
Taxol and cisplatin (cDDP) activate GADD153 gene expression differently. Cisplatin
Area of Science:
- Cellular biology
- Molecular oncology
- Signal transduction
Background:
- Cellular injury response pathways are crucial for cell survival and death.
- Growth arrest and DNA-damage-inducible 153 (GADD153) is upregulated by certain cellular injuries.
- GADD153 induction serves as a model for studying cellular injury response.
Purpose of the Study:
- To investigate the distinct mechanisms of GADD153 gene induction by taxol and cisplatin (cDDP).
- To identify the specific signaling pathways involved in GADD153 activation by these chemotherapeutic agents.
- To explore the potential of targeting these pathways to enhance drug efficacy.
Main Methods:
- Utilized a luciferase reporter assay to measure GADD153 promoter activity in human ovarian carcinoma cells.
- Quantified endogenous GADD153 mRNA levels using RT-PCR.
- Assessed the effect of the tyrosine kinase inhibitor, tyrphostin B46, on GADD153 induction and cell cytotoxicity.
Main Results:
- Taxol and cDDP differentially activated GADD153 promoter activity and mRNA expression.
- Cisplatin induced a significantly greater increase in GADD153 mRNA and promoter activity compared to taxol at equitoxic doses.
- Tyrphostin B46 inhibited cDDP-induced GADD153 activation and synergistically enhanced cDDP cytotoxicity, but had no effect on taxol.
Conclusions:
- Taxol and cDDP activate GADD153 through distinct signaling pathways.
- A tyrosine kinase pathway, inhibitable by tyrphostin B46, mediates GADD153 induction by cDDP.
- Inhibiting this pathway enhances cisplatin's cytotoxic effects, suggesting a therapeutic strategy.