Researchers studying an enzyme believed to play a role in allergy onset, instead have discovered its previously unknown role as a tumor suppressor that may be important in myeloproliferative diseases and some types of lymphoma and leukemia. Myeloproliferative diseases are a group of disorders characterized by an overproduction of blood cells by the bone marrow and include chronic myeloid leukemia. Lymphoma and leukemia are cancers of the blood.