TAL1 and acute lymphoblastic leukemia: Activation of TAL1, a basic helix-loop-helix (bHLH) transcription factor, is the most frequent gain-of-function mutation observed in T-ALL patients and is found in 40–60% of T-ALL cases resulted from chromosomal translocation (4–5%), interstitial chromosome deletion (25–30%), or an undefined mechanism (60%) (5–7).