Ref-1 and pSTAT3 were also characterised in the Nf1-Arfflox/flox;PostnCre mice that harbour combined genetic inactivation of Nf1 and the Cdkn2a alternate reading frame (Arf), which is deleted in 70–90% of NF1-associated ANNUBP and MPNST collectively.17 These mice spontaneously develop nerve sheath tumours histopathologically indistinguishable from human ANNUBP and which progress to MPNST with high penetrance. This evidence concerns the gene APEX1 and malignant peripheral nerve sheath tumor.