The first evidence for a role of Notch in tumorigenesis came from the finding that the acute T cell lymphoblastic leukemia translocation (T-ALL) t(7;9)(q34;q34.3) breakpoint generated the fusion of the gene for the ß chain of the T cell receptor at 7q34 and the TAN1/NOTCH1 gene at 9q34.3, giving rise to a constitutively active N-IC-like domain [49]. This evidence concerns the gene NOTCH1 and acute lymphoblastic leukemia.