To investigate the role of ERG in leukemia, we examined the expression level of ERG in multiple leukemia cell lines, including acute promyelocytic leukemia cell HL60, chronic myelogenous leukemia cell K562, acute monocytic leukemia cell THP1, and histiocytic lymphoma leukemia cell U937. The gene discussed is ERG; the disease is acute promyelocytic leukemia.