To investigate whether ENT1 is a key player for Ara-C chemoprotection observed when leukemia cells are incubated with HS5 SN, THP1 cells were incubated with human BMSC SN from HS5 in the presence or absence of a selective ENT1 small molecule inhibitor, Nitrobenzylthioinosine (NBMPR). The gene discussed is SLC29A1; the disease is leukemia.