PDGFB and neoplasm: To test the tumorigenicity of NG2 expressing cells in vivo, and to approximate the anatomical microenvironment of human DIPGs, we injected (100,000-150,000) NG2 expressing PDGFB mouse tumor neurospheres (Figure 5a-5c) orthotopically into the pons of 2-day old (P2) Balb/C mice and monitored for signs of tumor extension, including cerebellar ataxia [23].