SP1 and breast cancer: In conclusion, this study demonstrates that SREBP1 transcriptionally activates GS, promoting intracellular glutamine production and leading to increased O-GlcNAcylation of Sp1; in turn, O-GlcNAc-Sp1 transcriptionally upregulates the expression of SREBP1, resulting in a feedforward loop increasing lipogenesis and LD formation in liver and breast cancer cells (Figure 7).