SIRT4 and breast cancer: STAT3 is activated in breast cancer, and Y705 phosphorylation is elevated in MCF7 cells that are resistant to tamoxifen.11 Glutamine regulates cancer cell invasiveness via STAT3, and its deprivation significantly decreases the levels of STAT3 phosphorylation at Y705 in highly invasive ovarian cancer cells.27 Xia et al demonstrated that SIRT4 can induce SMCC7721 liver cancer cell aging by suppressing JAK2/STAT3 signaling, consistent with our observations in breast cancer.28 However, the molecular mechanisms controlling this were not discussed.