No abstract

The PML gene of acute promyelocytic leukemia (APL) encodes a cell-growth and tumor suppressor. PML localizes to discrete nuclear bodies (NBs) that are disrupted in APL cells, resulting from a reciprocal chromosome translocation t (15;17). Here we show that the nuclear localization of PML is also regulated by SUMO-3, one of the three recently identified SUMO isoforms in human cells. SUMO-3 bears similar subcellular distribution to those of SUMO-1 and -2 in the interphase nuclear body, which is colocalized with PML protein. However, both SUMO-2 and -3 are also localized to nucleoli, a region lacking SUMO-1. Immunoprecipitated PML protein bears SUMO-3 moiety in a covalently modified form, supporting the notion that PML is conjugated by SUMO-3. To determine the functional relevance of SUMO-3 conjugation on PML molecular dynamics, we suppressed SUMO-3 protein expression using a siRNA-mediated approach. Depletion of SUMO-3 markedly reduced the number of PML-containing NBa and their integrity, which is rescued by exogenous expression of SUMO-3 but not SUMO-1 or SUMO-2. The specific requirement of SUMO-3 for PML nuclear localization is validated by expression of SUMO-3 conjugation defective mutant. Moreover, we demonstrate that oligomerization of SUMO-3 is required for PML retention in the nucleus. Taken together, our studies provide first line of evidence showing that SUMO-3 is essential for PML localization and offer novel insight into the pathobiochemistry of APL.

Background/Aim: As the knowledgebase of acute myeloid leukemia (AML) has grown, classification systems have moved to incorporate these new findings. Methods: We assessed 32,941 patients with AML whose records are contained in the Surveillance, Epidemiology, and End Results (SEER) database. Results: Half of all patients diagnosed between 2001 and 2013 did not have a World Health Organization (WHO) classification. Acute promyelocytic leukemia and acute panmyelosis with myelofibrosis were associated with the longest leukemia-specific survival (110 and 115 months, respectively), and AML with minimal differentiation and acute megakaryoblastic leukemia with the shortest (30 and 28 months, respectively). For patients in the WHO groups AML not otherwise specified (AML-NOS) and AML with recurrent genetic abnormalities (AML-RGA), the risk of death was greater for older patients and less for married patients. Black patients with any type of AML-NOS also had a higher risk of death. Patients whose case of AML did not receive a WHO classification were older and this group had a higher risk of death when compared to patients with a WHO type of AML-NOS. Conclusion: Our findings highlight the divergent outcomes of patients with AML and the importance of using the WHO classification system and demographic factors to gauge their prognosis.