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Updated: Jun 11, 2026

Continuous Fluorescence-Based Endonuclease-Coupled DNA Methylation Assay to Screen for DNA Methyltransferase Inhibitors
06:07

Continuous Fluorescence-Based Endonuclease-Coupled DNA Methylation Assay to Screen for DNA Methyltransferase Inhibitors

Published on: August 5, 2022

Methylation patterns of genes coding for drug-metabolizing enzymes in tamoxifen-resistant breast cancer tissues

Sun Jung Kim1, Han-Sung Kang, So-Youn Jung

  • 1Department of Life Science, Dongguk University-Seoul, Seoul, 100-715, South Korea.

Journal of Molecular Medicine (Berlin, Germany)
|July 15, 2010
PubMed

Insights

Tamoxifen resistance in breast cancer is linked to increased methylation of the NAT1 gene, a drug-metabolizing enzyme. This hypermethylation correlates with lower NAT1 expression and higher tumor cell proliferation, suggesting a role in tamoxifen resistance.

Area of Science:

  • Oncology
  • Pharmacogenomics
  • Epigenetics

Background:

  • Tamoxifen is a crucial endocrine therapy for estrogen receptor-positive breast cancer.
  • Mechanisms of tamoxifen resistance are not fully understood, impacting treatment efficacy.
  • Epigenetic modifications, such as DNA methylation, are implicated in cancer development and drug resistance.

Purpose of the Study:

  • To investigate the association between DNA methylation patterns of drug-metabolizing enzyme genes and tamoxifen resistance in breast cancer.
  • To evaluate the expression levels of these genes in relation to methylation status and tamoxifen resistance.
  • To explore the correlation between gene methylation, expression, and markers of tumor proliferation.

Main Methods:

  • Analysis of methylation patterns and gene expression (mRNA) of COMT, CYP1A1, CYP2D6, NAT1, and SULT1A1 in tamoxifen-resistant and control breast cancer tissues.
  • Utilized bisulfite genomic sequencing, methylation-specific PCR, and reverse transcriptase polymerase chain reaction (RT-PCR).
  • Assessed Ki67 and cyclin D1 expression as markers of cell proliferation.

Main Results:

  • The NAT1 gene exhibited significantly higher methylation rates in tamoxifen-resistant tumors (62.2%) compared to control tumors (33.8%).
  • NAT1 mRNA expression was significantly lower in resistant tumors (28.6%) versus control tumors (65.2%) and was down-regulated in resistant tissues.
  • Higher percentages of Ki67 and cyclin D1 positive staining were observed in resistant cases, indicating increased proliferation.

Conclusions:

  • Increased methylation of the NAT1 gene is associated with tamoxifen resistance in breast cancer.
  • Hypermethylation of NAT1 may contribute to the development of tamoxifen resistance by reducing its expression.
  • These findings highlight the potential role of NAT1 epigenetic modifications in tamoxifen treatment failure.

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