Guanylate binding protein 2 (GBP2)has been considered as a possible controlling factor in tumor development.GBP2 gene expression and its promoter methylation status inboth plasma cfDNA and tumor tissues of ductal carcinoma breast cancer patientswere analyzed using SYBR green comparative Real-Time RT-PCR and, Methyl-specificPCR techniques, respectively in order to find a possible cancer-related marker.The results revealed that GBP2 gene expression and promotermethylation were inversely associated. This evidence concerns the gene GBP2 and breast carcinoma.