PTN and glioma: Our observation that PTN up-regulation in glioma likely occurs through broad amplification of chromosome 7, suggested as one of the earliest steps in gliomagenesis, prompted us to investigate if PTN is involved in transformation of neural progenitor cells, The RCAS/tv-a system is designed to induce targeted transformation of neural progenitor cells in vivo through viral delivery of oncogenes, allowing us to analyze if constitutive PTN-secretion is sufficient to induce glioma formation.