TP53 and neoplasm: While only one out of three of the mock-treated Ntv-a; LSL-Cas9; hUBC-CreERT2+/T mice injected with the RCAS-PDGFB and RCAS-Trp53-gRNA developed a low-grade tumor at 84 days, all the mice treated with tamoxifen were killed at earlier time due to high-grade gliomas (Fig. 3c, d).