SIRT1 and breast cancer: Similarly, other reports have shown that SIRT1 is overexpressed in malignant epithelial tumors,13 breast cancer,14 prostate tumors,15 soft tissue sarcomas,16 cutaneous T-cell lymphomas17 and melanoma,18 and high SIRT1 expression is associated with poor prognosis in diffuse B-cell lymphomas,19 ovarian and breast cancers.13,14 The significance of SIRT1 expression in tumor oncogenesis is, however, controversial due to the dual role of this sirtuin: on one side a negative effect on p53 function5,20 and on the other side its involvement in the maintenance of DNA integrity.