Abstract 5691: ESR1 methylation in plasma cfDNA of patients with high-grade serous ovarian cancer

Abstract

Abstract Introduction: ESR1 methylation is frequently observed in many types of solid malignancies, but few studies attempted to investigate ESR1 methylation status in ovarian cancer so far. We examined for the first time ESR1 methylation in plasma samples of high-grade serous (HGSC) ovarian cancer patients, using a novel real-time MSP assay. Materials and methods: We first developed and validated a highly specific and sensitive real-time MSP assay for ESR1 methylation. A commercially available 100% methylated standard was used as positive control in all experiments. We then evaluated ESR1 methylation in plasma (2mL) of 59 pre-surgery, mainly advanced stage HGSC patients. A control group of 51 plasma samples from healthy women was recruited for the evaluation of specificity of our assay. All cfDNA samples isolated from plasma were subjected to sodium bisulfite (SB) treatment and were then analyzed by real-time MSP for ESR1 methylation. For the normalization of the results, we used ACTB as a reference gene. The real-time PCR assay for ACTB was designed to amplify specifically SB treated DNA. Results: The real-time MSP assay is highly sensitive, as it detects down to 0.1% of ESR1 methylation in the presence of 99.9% non-methylated sequences. ESR1 methylation was detected in 18/59 (30.5%) high-grade serous ovarian patients, but only in 1/51 (2.0%) of healthy women. All results were obtained after normalization with ACTB as a reference gene. Conclusion: We report for the first time that ESR1 methylation can be detected in cfDNA of high-grade serous ovarian cancer patients, but not in healthy women. Further investigation is required to determine the clinical significance of ESR1 methylation status in cfDNA of HGSC patients. We also aim to evaluate our findings in a larger group of patients. Citation Format: Lydia Giannopoulou, Sophia Mastoraki, Areti Strati, Isaam Chebouti, Sabine Kasimir-Bauer, Evi S. Lianidou. ESR1 methylation in plasma cfDNA of patients with high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5691. doi:10.1158/1538-7445.AM2017-5691