TLR5, TLR7, and TLR9 are present in GL261 cells at low to undetectable levels, according to a different study by Grauer et al. Surprisingly, a single intratumoral injection of CpG ODN 1668 in C57BL/6 mice suppressed glioma development and cell proliferation in a cell-type-specific way. This evidence concerns the gene TLR9 and central nervous system cancer.