• Luiz Fernando de Queiroz, Marcelo Soares da Mota E Silva, Fernando Colonna Rosman, RosasSiane Lopes BittencourtSLB0000-0002-4814-0868Universidade Federal do Rio de Janeiro, Faculty of Medicine, Department of Clinical Medicine - Rio de Janeiro (RJ), Brazil., SouzaHeitor Siffert Pereira deHSP0000-0002-3647-7324Universidade Federal do Rio de Janeiro, Faculty of Medicine, Department of Clinical Medicine - Rio de Janeiro (RJ), Brazil., and Maria da Glória da Costa Carvalho.
• Universidade Federal do Rio de Janeiro, Faculty of Medicine, Postgraduate Program in Pathological Anatomy, Department of Pathology - Rio de Janeiro (RJ), Brazil.
• Rev Assoc Med Bras (1992). 2024 Jan 1; 70 (4): e20231358e20231358.

ObjectiveThis prospective study aimed to provide a comprehensive analysis of the methylation status of two pivotal genes, CDKN2A/p16INK4A (cyclin-dependent kinase inhibitor 2A) and RB1 (retinoblastoma transcriptional corepressor 1), in breast cancer patients.MethodsSamples were obtained from 15 women diagnosed with breast cancer and who underwent a total mastectomy. DNA was extracted from the tumor, non-tumor tissue, and peripheral blood (circulating cell-free DNA). The methylation pattern of cell-free DNA extracted from blood collected on the day of mastectomy was compared with the methylation pattern of cell-free DNA from blood collected 1 year post-surgery. The methylation analysis was carried out by sodium bisulfite conversion and polymerase chain reaction, followed by electrophoresis.ResultsMethylation of CDKN2A/p16INK4A was identified in 13 tumor samples and 12 non-tumor tissue samples. Two patients exhibited CDKN2A/p16INK4A methylation in the cell-free DNA of the first blood collection, while another showed methylation only in the cell-free DNA of the subsequent blood collection. Regarding RB1, 11 tumors and 8 non-tumor tissue samples presented methylation of the gene.ConclusionThis study presents a novel approach for monitoring breast cancer patients through the analysis of cell-free DNA methylation. This analysis can detect changes in methylation patterns before any visible sign of cancer appears in breast tissue and could help predict the recurrence of malignant breast tumors.

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