Despite the oncogenic effects of SIRT7, the high levels of this protein in breast cancer cells make them susceptible to the effects of fasting, where SIRT7 is phosphorylated at residue T263 by AMPK and then at residue S259 by GSK3β to prevent its binding to E3 ligase UBR5 and subsequent polyubiquitination and degradation. Here, SIRT7 is linked to breast cancer.