Among all genes that we identified as strongly differentially methylated between trastuzumab-resistant and trastuzumab-sensitive HER2-positive breast cancer patients, one of them, PRKACA, was reported as being higher expressed in breast cancer tissues of cases compared to controls in the study conducted by Merry and collaborators[50] and as being lower expressed in breast cancer tissues of cases compared to controls in the study of Gámez-Pozo et al.[47]. This evidence concerns the gene ERBB2 and breast cancer.