FTCD and Burkitt lymphoma: In several hematopoietic malignant cell types (erythroleukemia cells, Burkitt’s lymphoma cells, chronic myeloid leukemia cells), formimidoyltransferase cyclodeaminase (FTCD) and histidine ammonia lyase (HAL), which are enzymes involved in histidine catabolism consuming tetrahydrofolate, are associated with methotrexate sensitivity.