Previous reports revealed possible associations of transporters such as ABCG2 (BCRP1) 24, hENT1 (SLC29A1) 1, and hENT2 (SLC29A2) 25, activating factor such as deoxyguanosine kinase (DGUOK) 26, and inactivating factors such as 5′ nucleotidase (NT5C2) 1 and cytidine deaminase (CDA) 1 with Ara‐C sensitivity of leukemia cells. The gene discussed is BCRP1; the disease is leukemia.