This association is in agreement with reports in melanoma, as well as with a previous observation that NF1 loss is associated with MEK inhibitor sensitivity in approximately 30% of high-serum, adherent GBM cultures.23,34 Based on these data, we concluded that loss of NF1 expression confers ERK pathway dependence in GBM neurosphere cell lines. This evidence concerns the gene MAP2K7 and glioblastoma.