Aberrant activation of the NOTCH1 signaling cascade in T-ALL was first identified through the finding of a rare chromosomal translocation t(7; 9) (q34; q34.3) which determined the expression of a constitutively active form of NOTCH1 (Translocation associated notch protein 1; TAN-1) downstream of the TCRβ promoter [50]. Here, NOTCH1 is linked to acute lymphoblastic leukemia.