SIRT1 and cancer: In contrast, a moderate overexpression (∼4-fold) in cortical neurons confers a youthful gene transcription profile in old murine brains[38], and three to four-fold Sirt1 increase in the intestines of colon cancer prone mice[39], or in bone marrow lymphocyte progenitors of p53+/– lymphoma prone mice[38], protect both models from cancer.