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Published on: September 20, 2020
Single-Cell Image-Based Analysis Reveals Chromatin Changes during the Acquisition of Tamoxifen Drug Resistance
Han Zhao1, Li F Lin1, Joshua Hahn1
1Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Abstract:
Cancer drug resistance is the leading cause of cancer related deaths. The development of drug resistance can be partially contributed to tumor heterogeneity and epigenetic plasticity. However, the detailed molecular mechanism underlying epigenetic modulated drug resistance remains elusive. In this work, we systematically analyzed epigenetic changes in tamoxifen (Tam) responsive and resistant breast cancer cell line MCF7, and adopted a data-driven approach to identify key epigenetic features distinguishing between these two cell types. Significantly, we revealed that DNA methylation and H3K9me3 marks that constitute the heterochromatin are distinctively different between Tam-resistant and -responsive cells. We then performed time-lapse imaging of 5mC and H3K9me3 features using engineered probes. After Tam treatment, we observed a slow transition of MCF7 cells from a drug-responsive to -resistant population based on DNA methylation features. A similar trend was not observed using H3K9me3 probes. Collectively, our results suggest that DNA methylation changes partake in the establishment of Tam-resistant breast cancer cell lines. Instead of global changes in the DNA methylation level, the distribution of DNA methylation features inside the nucleus can be one of the drivers that facilitates the establishment of a drug resistant phenotype in MCF7.
Insights
Cancer drug resistance is a major cause of death. This study reveals that changes in DNA methylation patterns, not global levels, contribute to tamoxifen resistance in breast cancer cells.
Area of Science:
- Oncology
- Epigenetics
- Molecular Biology
Background:
- Cancer drug resistance, driven by tumor heterogeneity and epigenetic plasticity, is a critical challenge in cancer treatment.
- The precise molecular mechanisms of epigenetic drug resistance remain largely unknown.
- Tamoxifen (Tam) resistance in breast cancer is a significant clinical problem.
Purpose of the Study:
- To investigate the epigenetic alterations associated with tamoxifen resistance in MCF7 breast cancer cells.
- To identify key epigenetic features that differentiate drug-responsive from drug-resistant cell populations.
- To elucidate the role of DNA methylation and H3K9me3 in the development of tamoxifen resistance.
Main Methods:
- Systematic analysis of epigenetic changes in tamoxifen-responsive and -resistant MCF7 cell lines.
- Data-driven approach to identify distinguishing epigenetic features.
- Time-lapse imaging of 5-methylcytosine (5mC) and H3K9me3 using engineered probes after tamoxifen treatment.
Main Results:
- Distinct differences in DNA methylation and H3K9me3 heterochromatin marks were observed between tamoxifen-resistant and -responsive cells.
- Time-lapse imaging showed a gradual transition to drug resistance in MCF7 cells based on DNA methylation features following tamoxifen treatment.
- No similar trend was observed for H3K9me3 marks, suggesting a specific role for DNA methylation.
Conclusions:
- DNA methylation changes are implicated in the development of tamoxifen-resistant breast cancer cell lines.
- The spatial distribution of DNA methylation features within the nucleus, rather than global changes, may drive the acquisition of a drug-resistant phenotype.
- Epigenetic plasticity, particularly DNA methylation dynamics, is a key factor in overcoming cancer therapies.
