Epidermal Growth Factor Receptor Activation in Glioblastoma through Novel Missense Mutations in the Extracellular Domain

Background: Protein tyrosine kinases are important regulators of cellular homeostasis with tightly controlled catalytic activity. Mutations in kinase-encoding genes can relieve the autoinhibitory constraints on kinase activity, can promote malignant transformation, and appear to be a major determinant of response to kinase inhibitor therapy. Missense mutations in the EGFR kinase domain, for example, have recently been identified in patients who showed clinical responses to EGFR kinase inhibitor therapy. Methods and Findings: Encouraged by the promising clinical activity of epidermal growth factor receptor (EGFR) kinase inhibitors in treating glioblastoma in humans, we have sequenced the complete EGFR coding sequence in glioma tumor samples and cell lines. We identified novel missense mutations in the extracellular domain of EGFR in 13.6% (18/132) of glioblastomas and 12.5% (1/ 8) of glioblastoma cell lines. These EGFR mutations were associated with increased EGFR gene dosage and conferred anchorage-independent growth and tumorigenicity to NIH-3T3 cells. Cells transformed by expression of these EGFR mutants were sensitive to small-molecule EGFR kinase inhibitors. Conclusions: Our results suggest extracellular missense mutations as a novel mechanism for oncogenic EGFR activation and may help identify patients who can benefit from EGFR kinase inhibitors for treatment of glioblastoma

Epidermal Growth Factor Receptor Activation in Glioblastoma through Novel Missense Mutations in the Extracellular Domain

BACKGROUND: Protein tyrosine kinases are important regulators of cellular homeostasis with tightly controlled catalytic activity. Mutations in kinase-encoding genes can relieve the autoinhibitory constraints on kinase activity, can promote malignant transformation, and appear to be a major determinant of response to kinase inhibitor therapy. Missense mutations in the EGFR kinase domain, for example, have recently been identified in patients who showed clinical responses to EGFR kinase inhibitor therapy. METHODS AND FINDINGS: Encouraged by the promising clinical activity of epidermal growth factor receptor (EGFR) kinase inhibitors in treating glioblastoma in humans, we have sequenced the complete EGFR coding sequence in glioma tumor samples and cell lines. We identified novel missense mutations in the extracellular domain of EGFR in 13.6% (18/132) of glioblastomas and 12.5% (1/8) of glioblastoma cell lines. These EGFR mutations were associated with increased EGFR gene dosage and conferred anchorage-independent growth and tumorigenicity to NIH-3T3 cells. Cells transformed by expression of these EGFR mutants were sensitive to small-molecule EGFR kinase inhibitors. CONCLUSIONS: Our results suggest extracellular missense mutations as a novel mechanism for oncogenic EGFR activation and may help identify patients who can benefit from EGFR kinase inhibitors for treatment of glioblastoma

Exposure, entropion, and bilateral corneal ulceration in a newborn as a manifestation of chromosome 22 q11.2 duplication syndrome

Purpose: Chromosome 22q11.2 micro-duplication syndrome (MDS), is a rare autosomal dominant condition, with a highly variable phenotype that ranges from unremarkable and asymptomatic, to fatal due to cardiovascular defects. Hypertelorism, downslanting palpebral fissures, superior displacement of the eyebrows, and ptosis are the most commonly reported ocular manifestations. Here, we report a newborn with bilateral exposure, entropion, and corneal ulceration related to 22q11.2 MDS. Observation: A newborn girl presented with bilateral upper eyelid entropion, bilateral lower eyelid ectropion, and lagophthalmos. She subsequently developed bilateral corneal ulcers. Topical antibacterial drops, bandage contact lenses, medroxyprogesterone 1%, and fluorometholone 0.1%, together with partial tarsorrhaphy and correction of eyelid malposition, were used to treat the ulcers and address the underlying issues of exposure and entropion. Genetic testing revealed chromosome 22q11.2.MDS; further evaluation revealed systemic manifestations of this syndrome. The ocular surface healed well with gradual improvement of corneal opacification as well as bilateral partial tarsorrhaphy. Conclusion and importance: This report is the first that describes a newborn with 22q11.2 MDS presenting with sight-threatening corneal ulceration. Entropion, ectropion, and lagophthalmos were identified and treated, allowing for healing of the corneal surface. Genetic testing revealed a syndrome not known to be associated with eyelid abnormalities and corneal ulceration, but with other important systemic and ocular implications. Bilateral partial tarsorrhaphy should not be excluded as a treatment option for infants who fail more conservative measures for the treatment of exposure. Keywords: Chromosome 22q11.2 duplication syndrome, Corneal ulcer, Congenital entropion, Lagophthalmos, Partial tarsorrhaph

EGFR Missense Mutations in Glioblastoma Cluster in the Extracellular Domain and Are Associated with Increased <i>EGFR</i> Gene Dose

<div><p>(A) Location of missense mutations within the EGFR protein in a panel of 151 gliomas (132 glioblastomas, 11 WHO grade III gliomas, and eight glioblastoma cell lines). Each diamond represents one sample harboring the indicated mutation. Amino acid (AA) numbers are based on the new convention for EGFR numbering, which starts at the initiator methionine of pro-EGFR. Ligand-binding domains (I and III), cysteine-rich domains (II and IV), kinase domain (kinase), and the extracellular deletion mutant EGFRvIII [<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030485#pmed-0030485-b045" target="_blank">45</a>] are indicated as reference.</p> <p>(B) Increased <i>EGFR</i> gene dose in tumors harboring <i>EGFR</i> missense mutations. The array (left) shows a high-resolution view of Affymetrix 100K SNP array at the <i>EGFR</i> gene locus for ten glioblastoma tumors and three normal controls (sample numbers are indicated above each column). <i>EGFR</i> mutation and log₂ ratio (see <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030485#st2" target="_blank">Methods</a>) are indicated below each column. The plot (left) shows a comparison of <i>EGFR</i> gene copy number determination by SNP array (y-axis, EGFR log₂ ratios) and FISH (x-axis). AMP, amplified; NON-AMP, non amplified.</p> <p>(C) RT-PCR for <i>EGFRvIII</i> and full-length <i>EGFR</i> in 14 fresh-frozen glioblastoma tumors (see <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030485#st2" target="_blank">Methods</a>). The upper band represents full-length <i>EGFR</i> (1,044 bp), the lower band <i>EGFRvIII</i> (243 bp), and the inset shows glyceraldehyde-3-phosphate dehydrogenase <i>(GAPDH)</i> RT-PCR results.</p></div