ESR1 and breast cancer: In particular, AGR3 (Garczyk et al., 2015), CA12 (Li et al., 2019), CCDC170 (C6orf97; Yamamoto-Ibusuki et al., 2015), NDPKC (NME3; Wu et al., 2020), PEPT2 (SLC15A2; El Ansari et al., 2018), SUSD3 (Zhao et al., 2016) and ZIP6 (SLC39A6; Althobiti et al., 2021) have been linked to breast cancer in different studies and several of these genes have also been reported to interact or be associated with ER expression and function.