Infection of the nestin-expressing brainstem progenitors with PDGF-B and H3.3K27M resulted in half-of-the-mice developing grade III/IV tumors while similar infections with the combination of PDGF-B with either an empty vector or H3.3 wild-type (WT) resulted in the generation of only grade II tumors (32). Here, PDGFB is linked to infection.