In order to eliminate the possibility of a staining artifact, which could have accounted for the high expression level of p21CIP1 and H3K9Me3 in the biopsy specimens, we stained three breast tumor samples from patients who only underwent mastectomy without prior exposure to NAC and found high expression levels of both markers (SupplementaryFigure S3). The gene discussed is CDKN1A; the disease is breast neoplasm.