MAPK3 and leukemia: We thus generated Nfat1-deficient ICN1-driven T-ALLs carrying in addition conditional, floxed alleles of Nfat2 and Nfat4 and the Rosa-Cre-ERT2 transgene (RCT2) (see Materiel and Methods) to compare the leukemia initiating potential (LIC activity) of NFAT-proficient and NFAT-deficient T-ALL cells.