RB1 and acute lymphoblastic leukemia: Additional genetic events leading to leukemogenesis in T-ALL cases include loss of the tumor suppressor PTEN; loss of the cell-cycle inhibitors CDKN2A, RB, and CDKN1B; and increased expression of the transcription factors TAL1, LMO1, LMO2, TLX1, and TLX3 and the oncogene MYC [11, 40, 43].