ESR1 and breast cancer: In ERα-negative breast cancer cells, upon adiponectin treatment, Sp1 is phosphorylated by AMP-activated protein kinase (AMPK) and recruited on the responsive region of the Cyclin D1 promoter, causing the recruitment of a corepressor complex, the displacement of RNA Polomerase II, and the reduction Cyclin D1 transcriptional activity [55].