To confirm that the similarities in mENBT1 and hENBT1 function seen in the HEK293 over-expression models were not due to an artifact of the expression system, we also examined the characteristics of ENBT1-mediated [3H]6-MP uptake in a commonly used human leukemia cell model, MOLT-4, and a commonly used mouse leukemia cell model, L1210. The gene discussed is SLC43A3; the disease is leukemia.