ESR1 and breast cancer: Most of these results have been also described in vitro in ERα-negative breast cancer cells where adiponectin mainly serves to induce cell growth arrest and apoptosis regulating several proteins that govern cell cycle (i.e., p53, Bax, Bcl-2, c-myc and cyclin D1) [81,134,135,137,140,144,145,146] (Figure 2).