STEAP1 and prostate cancer: Currently, investigations of STEAP1 mainly focus on prostate cancers and show that expression of STEAP1 is elevated compared with normal prostate tissue (Li et al., 2004; Challita-Eid et al., 2007; Wong and Abubakar, 2010; Hayashi et al., 2011; Gomes et al., 2013, 2014a, 2018; Ihlaseh-Catalano et al., 2013; Whiteland et al., 2014).