TPO-increased proliferation and delayed apoptosis in patients with ALL and AML. (A) Incubation with TPO for 36 hours induced the proliferation of leukemia cells in 4 of 11 patients with c-mpl⁺ AML but in no patients with c-mpl^- AML or ALL (P < .05). (B) TPO incubation for 48 hours decreased the percentage of apoptotic cells in 5 of 11 patients with c-mpl⁺ AML but in no patients in other subgroups (c-mpl^- AML and ALL) (P < .05). The asterisks represent P < .05.