Epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor that plays a role in cell division, cell differentiation, and migration.1,2
Learn About EGFR Aberrations in Oncology: Amplification, Overexpression, and Mutation.
Dysregulation of EGFR has a causal role in the development and maintenance of certain human carcinomas.3
Amplification, Overexpression, Mutation
In cancer, the EGFR gene is often amplified, overexpressed, or mutated, resulting in abnormal signaling and malignant cellular behaviors.3
Amplification of the EGFR gene is among the most common genetic alterations in glioblastoma (GBM), occurring in approximately 50% of GBM tumors.3,9 EGFR amplification status is stable from GBM diagnosis to recurrence at a rate of 84% to 93% when treated with the current standard of care.10,11
EGFRvIII is another common mutation in GBM, occurring almost excusively in EGFR-amplified GBM. Approximately 25% of all GBMs harbor both EGFR amplification and the EGFRvIII mutation.3,17-19
Learn About EGFR in Glioblastoma.
The most commonly used diagnostic tools for clinical evaluation of EGFR gene amplification are fluorescence in situ hybridization (FISH) or colorimetric in situ hybridization (CISH).20
Fluorescence-tagged, sequence-specific probes (single-stranded DNA or RNA) are hybridized to complementary DNA or RNA sequences in cells or tissues.21-24
Colorimetric in situ hybridization, also known as chromogenic in situ hybridization (CISH), is similar to FISH, but probes are labeled with a chromogen instead of fluorescence.
Dual in situ hybridization (DISH) is a form of CISH that utilizes 2 differentially labeled probes that are cohybridized and visualized on the same slide.
In addition to FISH and CISH/DISH, a number of other methods are available for the clinical evaluation of EGFR copy number, directly or indirectly.
Next-generation sequencing (NGS) technology allows high-throughput sequencing of millions of DNA templates in a single reaction with multiple patient samples. Applications include sequencing of the whole genome or of targeted protein-coding regions.22
Targeted NGS/exome sequencing20,22,34
Potential drawbacks include34:
PCR allows the rapid amplification of a specific DNA fragment from a complex pool of DNA.35 Double-stranded DNA is denatured, sequence-specific primers are annealed to the single DNA strands, and the primers are elongated by DNA polymerase.35,36
IHC and IF semiquantitatively measure protein levels only, and do not measure EGFR gene amplification. Antibodies are bound to a specific antigen on a protein of interest in fixed cells or tissues and then visualized.38,39
Potential drawbacks include38,39:
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