Abstract 4813: DNA methylation of tumor suppressor and metastasis suppressor genes in primary tumors, circulating tumor cells and cell free DNA in the same breast cancer patients

Abstract

Abstract Introduction: Blood based specimens such as Circulating Tumor Cells (CTCs) and cell free DNA (cfDNA) provide a very promising and non-invasive liquid biopsy approach. In our study, we first compared the promoter methylation status of BRMS1 and SOX17 genes in DNA samples isolated from primary tumors, matched CTCs and cfDNA isolated from the same breast cancer patients. Methods: We first developed and validated real time Methylation Specific PCR (MSP) assays for studying BRMS1, CST6 and SOX17 promoter methylation. We further analysed 165 paired DNA samples isolated from: a) the EpCAM positive CTC fraction from 92 operable, 61 metastatic breast cancer patients and 12 healthy individuals, b) the corresponding plasma from the same individuals. All CTC were also checked for CK-19 mRNA expression by RT-qPCR. Additionally, we investigated the promoter methylation status of BRMS1 and SOX17 in corresponding primary tumors (n=75). Results: In operable breast cancer, comparison of SOX17 promoter methylation status in CTCs and corresponding cfDNA revealed a direct association (P = 0.001), while it was also highly correlated with CK-19 mRNA expression (P=0.006). In patients with verified metastasis, there was a direct connection between SOX17 promoter methylation in CTCs and cfDNA (P=0.046), while SOX17 promoter methylation in cfDNA was highly correlated with CK-19 mRNA expression (P=0.04). Our results are shown below Conclusion: Our findings indicate a direct connection between SOX17 promoter methylation in CTCs and cfDNA both in patients with operable breast cancer, and verified metastasis. resultsBreast CancerGenesCTC fractioncfDNAFFPEsOperable (N=92)CST624/92(26.1%)33/92(35.9%)not analyzedSOX1719/92(20.7%)24/92(26.1%)26/43(60.5%)BRMS120/92(21.7%)22/92(23.9%)19/43(44.1%)Verified metastasis (N=61)CST621/61(34.4%)26/61(42.6%)not analyzedSOX1726/61(42.6%)22/61(36.1%)21/32(65.6%)BRMS126/61(42.6%)4/61(6.6%)5/32(15.6%) Citation Format: Maria Chimonidou, Areti Strati, Nikos Malamos, Vassilis Georgoulias, Evi Lianidou. DNA methylation of tumor suppressor and metastasis suppressor genes in primary tumors, circulating tumor cells and cell free DNA in the same breast cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4813. doi:10.1158/1538-7445.AM2014-4813