BMI1 and colorectal cancer: Kreso et al. first characterized PTC 209 as a pharmacological inhibitor of Bmi1 in a colorectal cancer model and described the loss of stemness and growth inhibition in vitro of human colorectal CSCs upon PTC 209 treatment, as well as inhibition of tumor growth in vivo when nude mice with tumor cell xenografts were treated with the Bmi1 inhibitor [20].