Playing both sides: nucleophosmin between tumor suppression and oncogenesis

Nucleophosmin (NPM) is frequently mutated in acute myeloid leukemias and is thought to act as both a proto-oncogene and a tumor suppressor. Although genetic and molecular evidence has shed light on the mechanisms of NPM-mediated tumor suppression, the potential role of NPM mutants as oncogenes remains ill defined. Now, new data provide a straightforward mechanism for this latter function, as NPM is shown to regulate the stability and the function of MYC. Remarkably, the same leitmotif of "placing a critical cell regulator in the wrong place at the wrong time" appears to underscore all the cancer-promoting activities of mutated NPM.