Whereas high Id4 expression in a B-cell acute lymphoblastic leukemia [27] and B-cell precursor acute lymphoblastic leukemia(BCP-ALL [28]) due to t(6;14) (p22;q32) chromosomal translocation and in bladder [29] and rat mammary gland carcinomas [30] suggests that it may have pro-tumor activity also. The gene discussed is ID4; the disease is acute lymphoblastic leukemia.