These conclusions stem from two sets of data showing delayed leukemia onset in (i) TEL-JAK2 transgenic mice deficient in RelB, as compared to RelB-proficient littermates, and (ii) lethally irradiated RelB-deficient mice reconstituted with TEL-JAK2 transgenic bone marrow, as compared to similarly reconstituted RelB-proficient littermates. This evidence concerns the gene JAK2 and leukemia.