BMP4 and breast cancer: In addition to breast cancer, BMP4 promotes tumor progression, angiogenesis, and metastasis in multiple cancer types (Rothhammer et al., 2007; Maegdefrau et al., 2009; Martínez et al., 2017; Zhou et al., 2018; Ju et al., 2019; Deng et al., 2020), but opposite and conflicting results have also been reported (Cao et al., 2014; Zhao et al., 2019).