Extensive studies have uncovered an important oncogenic role for PIWIL1 in cancer tumor initiation, progression and metastasis (Liu et al., 2006, 2014; Siddiqi et al., 2012; Wang et al., 2012, 2017; Zhao et al., 2012; Liang et al., 2013; Wang D.W. et al., 2014; Wang X. et al., 2014; Chen et al., 2015a; Li et al., 2015, 2020; Xie et al., 2015, 2018; Yang et al., 2015; Cao et al., 2016; Araújo et al., 2018; Gao et al., 2018; Jiang et al., 2020; Shi et al., 2020; Zhou et al., 2020; Table 2 and Figure 4). The gene discussed is PIWIL1; the disease is cancer.