To discriminate between OCI/AML cells and to evaluate if the absence of truncated cytoplasmic APE1 in extracts of OCI/AML2 cells [13] was due to a differential extent of protease activity in this line, with respect to OCI/AML3, we performed and compared proteolysis experiments with cells extracts from OCI/AML2 and OCI/AML3 cell lines. The gene discussed is APEX1; the disease is acute myeloid leukemia.