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A microarray-based, integrated approach to identify novel regulators of cancer drug response and apoptosis
Arndt Brachat1, Benoit Pierrat, Alexandros Xynos
1Oncology Research, Novartis Pharma AG, CH-4002 Basel, Switzerland.
Abstract:
DNA microarrays are powerful tools for the analysis of gene expression on a genomic scale. The importance of individual regulatory events for the process under study can however not be deduced unequivocally without additional experiments. We devised a strategy to identify central regulators of cancer drug responses by combining the results of microarray experiments with efficient methods for phenotypic testing of candidate genes. We exposed murine FL5.12 pro-B cells to cisplatin, camptothecin, methotrexate or paclitaxel, respectively and analysed the patterns of gene expression with cDNA microarrays. Drug-specific regulatory events as well as intersections between different apoptotic pathways, including previously studied responses to staurosporine and interleukin-3 (IL-3) deprivation, were identified. Genes shared by at least three pathways were chosen for further analysis. Ectopic expression of three such genes, TEAP, GP49B, and Lipin1 was found to have an anti-proliferative effect on pro-B cells. Interestingly, we identified hemoglobin alpha as a strong pro-apoptotic regulator. While hemoglobin-expressing cells were growing normally in the presence of IL-3, they displayed accelerated apoptosis with similar kinetics as Bax overexpressing cells upon IL-3 removal. The pro-apoptotic effect of hemoglobin was suppressed by Bcl-2 and was characterized by enhanced stimulation of caspase activity.
Insights
This study identifies key genes regulating cancer drug responses by combining gene expression analysis with functional testing. Hemoglobin alpha emerged as a potent pro-apoptotic regulator, influencing cell death pathways.
Area of Science:
- Molecular Biology
- Genomics
- Cancer Research
Background:
- DNA microarrays enable large-scale gene expression analysis but require further experiments to pinpoint regulatory events.
- Identifying central regulators of cancer drug responses is crucial for understanding treatment efficacy and resistance.
Purpose of the Study:
- To develop a strategy for identifying key regulators of cancer drug responses.
- To combine microarray gene expression data with phenotypic screening of candidate genes.
Main Methods:
- Murine FL5.12 pro-B cells were treated with various chemotherapy drugs (cisplatin, camptothecin, methotrexate, paclitaxel).
- Gene expression patterns were analyzed using cDNA microarrays.
- Candidate genes were further analyzed through ectopic expression and functional assays, including apoptosis studies.
Main Results:
- Drug-specific regulatory events and intersections between apoptotic pathways were identified.
- Genes common to at least three pathways were selected for further investigation.
- Ectopic expression of TEAP, GP49B, and Lipin1 showed anti-proliferative effects.
- Hemoglobin alpha was identified as a potent pro-apoptotic regulator, accelerating apoptosis upon IL-3 deprivation, an effect suppressed by Bcl-2 and involving caspase activation.
Conclusions:
- A combined approach of gene expression profiling and functional screening effectively identifies critical regulators of drug response.
- Hemoglobin alpha plays a significant role in apoptosis, highlighting its potential as a therapeutic target or biomarker in cancer.
- Understanding these regulatory networks can inform the development of novel cancer therapies.