EPIGENETIC PROFILING: ANALYSIS OF DNA METHYLATION AND DEMETHYLATION PATTERNS IN TRIPLE-NEGATIVE BREAST CANCER

Abstract

Introduction: TNBC is a highly advanced, molecular subtype of breast cancer, characterized by lack of gene expression of the estrogen receptor, progesterone receptor and HEGF-2 (human epidermal growth factor receptor-2). Additionally, patients with TNBC, the absence of particular therapeutic targets are associated with unfavorable clinical results, while the high risk of metastasis and recurrence. There is increasing evidence that epigenetic modifications, such as methylation of DNA and demethylation events, are important factors in the spread and development of TNBC, also in metastasis and treatment resistance. While active demethylation of DNA through 5-hydroxymethyl-cytosine (5-hmC) has been connected to chromatin remodeling and gene regulation, DNA methylation through 5-methyl-cytosine (5-mC) is a crucial mechanism for silencing genes. Tumor suppressor genes, oncogenic signaling pathways, and all cellular differentiation pathways have been linked to the abnormal levels of 5-mC and 5-hmC found in TNBC samples. Method: The research investigated how DNA methylation and demethylation markers in tumor tissue affect the response of TNBC patients to neoadjuvant chemotherapy (NACT) compared to those who did not receive NACT, while exploring the relationship between 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC), revealing new insights into the predictive significance of these epigenetic indicators. The study comprised 40 female patients with TNBC, where 15 underwent neoadjuvant chemotherapy (NACT) and 25 did not. Global DNA methylation and demethylation levels were measured using an ELISA-based technique to investigate the content of 5-mC and 5-hmC levels in DNA extracted from biopsy samples of patients receiving NACT and postoperative tissues from those without NACT. Results: There was a significant positive correlation found between two global methylation markers (rs=0.929, p < 0.0001).Favorable association between 5-hmc and 5-mC was observed (rs= 0.017, p < 0.951 and rs= 0.069, p < 0.743, respectively). Hence we propose that 5-methylcytosine and 5-hydroxymethylcytosine to be consider as key molecular markers of pathogenesis of TNBC. Moreover, the findings support epigenetic interventions aimed to restore DNA methylation dynamics to a "normal" state.