Our in vivo data, showing delayed mammary tumor development and increased survival in MMTV-PyMT+/−; Sirt6+/− mice as compared to MMTV-PyMT+/−; Sirt6+/+ animals, are in line with the previously reported adverse prognostic significance of high SIRT6 expression in BC [16, 17]. This evidence concerns the gene SIRT6 and breast cancer.