Momilactone B also induced G1 arrest in the cell cycle and apoptosis in the human leukemia U937 cell line through the suppression of pRB phosphorylation and the induction of the kinase inhibitor p21 [102], and it induced apoptosis in human leukemia T cells through the activation of caspase [103] and in human breast cancer cells through signal transducer and activator of transcription 5 and a caspase-3-dependent pathway [104]. This evidence concerns the gene RB1 and leukemia.