Epidermal growth factor receptor signaling pathways are associated with tumorigenesis in the Nf1: p53 mouse tumor model

The human disease neurofibromatosis type 1 (NF1) is caused by mutations in the NF1 gene, and is characterized by the formation of benign and malignant tumors of the peripheral nervous system. We have shown previously that aberrant expression of the epidermal growth factor receptor (EGFR) is a common feature of human NF1-related tumor development in humans and in NF1 animal models. One recent approach taken to investigate the changes associated with NF1 tumor formation is the development of the Nf1:p53 mouse tumor model. Here, we examined a series of tumor cell lines derived from Nf1:p53 mice for their expression of EGFR family members. Immunoblotting analyses revealed that 23 of the 24 cell lines examined express the EGFR, and 24 of 24 express the related tyrosine kinase erbB2, whereas erbB3 was detected in only 6 of 24. All of the cell lines expressing EGFR responded to epidermal growth factor (EGF) by activation of the downstream signaling pathways, mitogen-activated protein (MAP)/extracellular signal-regulated kinase kinase/MAP kinase, and phosphatidylinositol 3′-kinase (PI3k)/AKT. Growth of the cell lines was greatly stimulated by EGF in vitro and could be blocked by an antagonist of the EGFR. In addition, inhibition of the PI3k pathway potently inhibited the EGF-dependent growth of these cell lines, whereas inhibition of the MAP/extracellular signal-regulated kinase kinase/MAP kinase pathway had more limited effects. We conclude that EGFR expression is a common feature of the Nf1:p53 tumor cell lines and that inhibition of this molecule or its downstream target PI3k, may be useful in the treatment of NF1-related malignancies.