ESR1 and breast cancer: While the expression of GR is decreased during breast cancer development (Perou et al, 2000; Sørlie et al, 2001; Lien et al, 2006; Conde et al, 2008; Buxant et al, 2010), studies have shown that GR activation by GCs can inhibit cell proliferation in estrogen receptor (ER)‐positive breast cancer (Tonsing‐Carter et al, 2019).