FTCD and leukemia: We find an increased dependency of leukemia cell lines on MTHFD1 (cytosolic methylene-tetrahydrofolate dehydrogenase) where the expression of MTHFR (methylene-THF reductase) that consumes 5,10-methylene-THF is high, and the expression of FTCD (formimidoyltransferase cyclodeaminase) that produces 5,10-methylene-THF as part of histidine catabolism is low (Fig. 4a).