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DOK7 CpG hypermethylation in blood leukocytes as an epigenetic biomarker for acquired tamoxifen resistant in breast cancer



Breast cancer (BC) is among the most common cause of cancer 10.4% and one of the leading causes of death among 20–50 years old women in the world. Tamoxifen drug is the first line therapy for BC however tamoxifen resistance (TR) has shown in 30–50% of cases that may face BC recurrence. Hence, TR early detection reduces BC recurrence and fatalities. The epigenetic alteration that happens by hypermethylation of tumor suppressor genes and hypomethylation of oncogenes has been suggested to be useful in early cancer or drug resistance diagnosis.


This is the first study to investigate DOK7 CpG hypermethylation in blood leukocytes of 31 TR (ER+) BC compared to 29 tamoxifen sensitive BC to evaluate DOK7 as a potential TR biomarker. DNA was extracted from blood samples of all participants and MSRE-PCR and real-time PCR were used for quantification of CpG methylation alterations.


The means of DOK7 CpG hypermethylation were obtained as 85.03%, 29.1% and 57.34% in TR, TS and normal control respectively. Significant hypermethylation were found among TR vs. TS (p < 0.001), TS vs. normal (p < 0.001) and TR vs. normal controls (p < 0.03). Online databases expression and survival analysis of DOK7 showed increasing expression in TS groups vs. TR groups which have consistency with our methylation alteration results. The sensitivity and specificity of the TR epigenetic test were determined using ROC analysis showed 89.66% and 96.77% respectively and showed that 37.5% above hypermethylation is at risk for TR and breast cancer recurrence.


There is a significant difference in the methylation ratio of DOK7 between tamoxifen resistant and tamoxifen sensitive groups that may be useful in the early diagnosis of tamoxifen resistance in BC cases and cancer recurrence prevention.

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This work was carried out at the National Institute of Genetic Engineering and Biotechnology (NIGEB), and the authors would like to express their appreciation to NIGEB. We are grateful to Arash Moradi, a student at the National Institute of Genetic Engineering and Biotechnology (NIGEB) for his participation in the study.


Our study was supported by grants number 766 from National Institute of Genetic Engineering and Biotechnology (NIGEB).

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SAA designed experiments, support and helped write the manuscript; EG carried out some experiments and write the manuscript; NR carried out some experiments; NN and MT contributed to sample collection and patients data extraction.

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Correspondence to Seyed Ahmad Aleyasin.

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Gowdini, E., Aleyasin, S.A., Ramezani, N. et al. DOK7 CpG hypermethylation in blood leukocytes as an epigenetic biomarker for acquired tamoxifen resistant in breast cancer. J Hum Genet 68, 33–38 (2023).

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