STEAP1 and breast cancer: Six-transmembrane epithelial antigen of prostate-1 is reportedly aberrantly regulated in numerous cancers, including prostate cancer, Ewing’s sarcoma, breast cancer and colorectal cancer, and is associated with the prognosis of cancer patients (Grunewald et al., 2012c; Ihlaseh-Catalano et al., 2013; Gomes et al., 2014; Lee et al., 2016; Barroca-Ferreira et al., 2018; Nakamura et al., 2019; Sun et al., 2019; Xie et al., 2019).