7-Hydroxymethotrexate formation in a human lymphoblastic cell line.

7-Hydroxymethotrexate is a major metabolite of methotrexate in patients undergoing chemotherapy with this drug. It has now been demonstrated that when cultures of CCRF-CEM, a human lymphoblastic cell line, are incubated in the presence of 100 microM methotrexate, significant quantities of 7-hydroxymethotrexate are formed. This finding is relevant to clinical use of the drug since it is now clear that during the treatment of acute lymphocytic leukemia conversion of methotrexate to the relatively inactive 7-hydroxy derivative probably occurs not only in the liver but also in the target cells.