The activation of oncogenic transcription factors including the basic helix-loop-helix genes (bHLH) TAL1, TAL2, LYL1, and OLIG2 (BHLHB1); TLX1 (HOX11), TLX3 (HOX11L2), NKX2-1, NKX2-2, and NKX2-5; the LIM-only domain genes LMO1 and LMO2 is also a hallmark of T-ALL. This evidence concerns the gene OLIG2 and acute lymphoblastic leukemia.