Maspin is not required for embryonic development or tumour suppression

Maspin (SERPINB5) is accepted as an important tumour suppressor lost in many cancers. Consistent with a critical role in development or differentiation maspin knockout mice die during early embryogenesis, yet clinical data conflict on the prognostic utility of maspin expression. Here to reconcile these findings we made conditional knockout mice. Surprisingly, maspin knockout embryos develop into overtly normal animals. Contrary to original reports, maspin re-expression does not inhibit tumour growth or metastasis in vivo , or influence cell migration, invasion or survival in vitro . Bioinformatic analyses reveal that maspin is not commonly under-expressed in cancer, and that perturbation of genes near maspin may in fact explain poor survival in certain patient cohorts with low maspin expression. A role for the serpin maspin has been described in both development and cancer. In this study, the authors demonstrate that maspin knockout mice develop normally and that maspin does not function as a tumour suppressor, suggesting that another gene at the maspin locus may be responsible for this activity.