PBK and breast cancer: Pbk is normally expressed in several select tissues (Abe et al,2000; Zhu et al,2007) and a subset of cancers including breast cancer, ovarian cancer, and leukemia (Park et al,2006; Ikeda et al,2016; Ishikawa et al, 2018), but is mainly restricted to non‐dividing tissues (Gaudet et al,2000; Zhao et al,2001).