TP53 and glioblastoma: Using two representative mouse M-GBM cell lines (1861 and 4622), which lack Nf1 and Tp53 expression [17], and two representative mouse proneural GBM cell lines ((2)61 and (5)54), which retain neurofibromin expression (Figure 1C) [18], we found that Ccl5 levels were elevated in the culture medium of mouse M-GBM cells relative to PN-GBM cells, as well as to wild-type primary mouse astrocytes (Figure 1D).