As expected , tumors and cell lines with NF1 defects lacked mutations in KRAS or BRAF but showed Ras pathway activation based on immunohistochemical detection of phosphorylated MAPK ( primary tumors ) or increased levels of GTP-bound Ras ( cell lines ) .
O O O B-DiseaseOrPhenotypicFeature O O O O B-GeneOrGeneProduct O O O O B-GeneOrGeneProduct O B-GeneOrGeneProduct O O B-GeneOrGeneProduct O O O O O O O O B-GeneOrGeneProduct O O B-DiseaseOrPhenotypicFeature O O O O O B-ChemicalEntity B-GeneOrGeneProduct O O O O O