CD34 and acute lymphoblastic leukemia: Recently this stromal cell line had also been genetically manipulated to constitutively express the human NOTCH ligand DL1, allowing leukemic blasts from T-ALL patients to proliferate [14] and also normal CD34+CD7− human progenitors to differentiate into T cells [13] as originally described for OP9 and S17 cell lines for mouse and human progenitor cells [15], [17], [21].