This potential role of Serpine2/PN-1 during medulloblastoma development in Ptch1Δ/+ mice was assessed genetically by inactivating one or both copies of the Serpine2/Pn-1 gene using a constitutive loss-of-function (Pn-1Δ) allele [38]. The gene discussed is SERPINE2; the disease is medulloblastoma.