GENE-45. DETAILED BREAKPOINT ANALYSES IMPLY THAT EGFRvIII DELETIONS ARE GENERATED BY DIFFERENT GENOMIC REARRANGEMENTS OF AMPLIFIED FULL LENGTH EGFR
Year: 2017
Type: conference-abstract
Abstract: Epidermal growth factor receptor (EGFR) variant III (vIII), which has an extracellular truncation encompassing exons two to seven, is the most common EGFR mutant in glioblastoma and is associated with aggressive tumor growth. Owing to the long intron one of this gene (123Kb), the breakpoints are highly variable between patient samples and have proven difficult to map. Additionally, mechanisms causing these deletions have not been characterized. Here we determined the presence of EGFRvIII and accompanying breakpoint structures for 29 glioblastoma samples using a combination of quantitative polymerase chain reaction (qPCR) screening, mapping PCR and Sanger sequencing. Further, to obtain information regarding the allele of origin for EGFRvIII, single nucleotide polymorphism (SNP) sites in amplified non-vIII EGFR and EGFRvIII transcripts were determined. In 12 out of 29 patient samples, EGFR was amplified and copy number differences between inside and outside regions of the vIII deletion revealed at least one vIII-indicative PCR product in eight of the patient samples. Eight different EGFRvIII breakpoints were detected in six tumors among eight qPCR-positive samples using our mapping PCR procedure. The breakpoint sequences showed features of different genomic rearrangements such as insertions, duplications and inversions. EGFRvIII transcripts in two samples that had two different breakpoint junctions had homogeneous SNP compositions identical to amplified non-vIII EGFR expressed in each patient. Additionally, using patient-specific primers, based on breakpoint mapping results from a single patient, EGFRvIII products were detected in DNA isolated from this patient’s cerebrospinal fluid. In conclusion, EGFRvIII breakpoints are highly patient specific, show traces of different genomic rearrangements, and multiple vIII breakpoint structures may be generated from amplified non-vIII EGFR in each patient.
Source: Neuro-Oncology
Institutions: University of California San Diego, Ludwig Cancer Research
Language: English
Subfield: Genetics (clinical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2767681758