In addition, measurement of the proliferation rate of tumors initiated with PDGF-B and H3.3K27M vs. PDGF-B and H3.3 WT or PDGF-B and empty vector demonstrates that H3.3K27M significantly increases the proliferation rate of PDGF-B driven brainstem gliomas. Here, PDGFB is linked to brain stem glioma.