Through microarray analyses, we identified the Mpped2 gene as differentially expressed in two neuroblastoma cell lines induced to differentiation with all-trans retinoic acid. Mpped2 codes for a new metallophosphodiesterase protein, the expression of which inhibits cell proliferation and soft agar colony formation in SH -SY5Y cells. This inhibition is concomitant to an increased proportion of the cells in G0/G1 phase and enhanced caspase 3 activation, effects not seen for the other phosphodiesterases. A Mpped2-null mutation (H67R) abrogates these functions, which indicates that the biochemical activity of Mpped2 is advantageous for cancer suppression. Expression analyses in the "Los Angeles" and "Essen" neuroblastoma gene-array data sets show that increased expression of Mpped2 is associated with good patient prognosis according to Kaplan-Meier analyses. Tumorigenic assays in mice show that overexpression of Mpped2 improves survival rate, substantially impairs tumor growth and induces neuronal differentiation. Altogether, these data show that Mpped2 expression impairs neuroblastoma tumorigenesis, and they establish a basis for future therapeutic applications.