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Adaphostin toxicity in a sensitive non-small cell lung cancer model is mediated through Nrf2 signaling and heme
Nicole D Fer1, Robert H Shoemaker, Anne Monks
1Laboratory of Functional Genomics, SAIC-Frederick Inc., NCI-Frederick, 1050 Boyles Street, Frederick, MD 21702, USA.
Background:
Preclinical toxicity of adaphostin has been related to oxidative stress. This study investigated the regulatory mechanism underlying adaphostin induction of heme oxygenase 1 (HMOX1) which plays a significant role in modulation of drug-induced toxicity in the non-small cell lung cancer cell line model, NCI-H522.
Methods:
The transcriptional response of NCI-H522 to adaphostin prominently involved oxidative stress genes, particularly HMOX1. Reactive oxygen species (ROS) involvement was additionally established by generation of ROS prior to modulation of adaphostin-toxicity with antioxidants. To identify up-stream regulatory elements of HMOX1, immunofluorescence was used to evaluate nuclear translocation of the transcription factor, NF-E2-related factor 2 (Nrf2), in the presence of adaphostin. The PI3-kinase inhibitor, wortmannin, was employed as a pharmacological inhibitor of this process.
Results:
Generation of ROS provided a substantial foundation for the sensitivity of NCI-H522 to adaphostin. However, in contrast to leukemia cell lines, transcriptional response to oxidative stress was associated with induction of HMOX1, which was dependent on nuclear translocation of the transcription factor, Nrf2. Pretreatment of cells with wortmannin inhibited translocation of Nrf2 and induction of HMOX1. Wortmannin pretreatment was also able to diminish adaphostin induction of HMOX1, and as a consequence, enhance the toxicity of adaphostin to NCI-H522.
Conclusions:
Adaphostin-induced oxidative stress in NCI-H522 was mediated through nuclear translocation of Nrf2 leading to upregulation of HMOX1. Inhibition of Nrf2 translocation by wortmannin inhibited this cytoprotective response, and enhanced the toxicity of adaphostin, suggesting that inhibitors of the PI3K pathway, such as wortmannin, might augment the antiproliferative effects of adaphostin in solid tumors that depend on the Nrf2/ARE pathway for protection against oxidative stress.
Insights
Adaphostin induces oxidative stress in lung cancer cells via Nrf2 and HMOX1. Inhibiting this pathway with wortmannin enhances adaphostin toxicity, suggesting potential combination therapies.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Preclinical adaphostin toxicity is linked to oxidative stress.
- Heme oxygenase 1 (HMOX1) modulates drug-induced toxicity.
- This study focuses on NCI-H522 non-small cell lung cancer cells.
Purpose of the Study:
- Investigate the mechanism of adaphostin-induced HMOX1 expression.
- Determine the role of oxidative stress and Nrf2 in this process.
- Explore therapeutic strategies to enhance adaphostin efficacy.
Main Methods:
- Assessed transcriptional response to adaphostin in NCI-H522 cells.
- Measured reactive oxygen species (ROS) generation.
- Utilized immunofluorescence to track Nrf2 nuclear translocation.
- Employed wortmannin, a PI3-kinase inhibitor, to block Nrf2 translocation.
Main Results:
- Adaphostin induced ROS generation and HMOX1 expression in NCI-H522 cells.
- HMOX1 induction was dependent on Nrf2 nuclear translocation.
- Wortmannin inhibited Nrf2 translocation and HMOX1 induction.
- Wortmannin pretreatment enhanced adaphostin's toxicity to NCI-H522 cells.
Conclusions:
- Adaphostin-induced oxidative stress in NCI-H522 cells is mediated by Nrf2-dependent HMOX1 upregulation.
- Inhibition of Nrf2 translocation by wortmannin abrogates this protective response.
- PI3K pathway inhibitors may augment adaphostin's antiproliferative effects in solid tumors reliant on the Nrf2/ARE pathway.