Although it has been widely reported that PTC-209 exerts its activity through downregulation of Bmi-1 protein level in various types of cancer cells (Kreso et al., 2014; Bolomsky et al., 2016; Yong et al., 2016; Alzrigat et al., 2017; Wang et al., 2017), there are still controversy regarding the exact mechanism through which it downregulates Bmi-1. Here, BMI1 is linked to cancer.