BMI1 and fibrosarcoma: It has been reported that another BMI-1 inhibitor PTC596, which is efficacious in xenograft tumor models of glioblastoma, fibrosarcoma and leukemia, induces CDK1/2 binding to BMI-1 and CDK1/2-mediated phosphorylation of BMI-1 at N-terminal sites, leading to degradation of BMI-1 [28].