Detection and characterization of classical and “uncommon” exon 19 Epidermal Growth Factor Receptor mutations in lung cancer by pyrosequencing
1 Divisions of Pathology, University of Torino, Regione Gonzole 10, Torino, Orbassano, 10043, Italy
2 Department of Clinical and Biological Sciences, Medical Genetics, University of Torino, Regione Gonzole 10, Torino, Orbassano, 10043, Italy
3 Pathology Unit, ASLCN2, Cuneo, Alba, Italy
4 Oncology Unit, ASLTO5, Torino, Carmagnola, Italy
5 Department of Oncology, Medical Oncology, University of Torino, Regione Gonzole 10, Torino, Orbassano, 10043, Italy
BMC Cancer 2013, 13:114 doi:10.1186/1471-2407-13-114Published: 13 March 2013
The management of advanced stage non-small cell lung cancer is increasingly based on diagnostic and predictive analyses performed mostly on limited amounts of tumor tissue. The evaluation of Epidermal Growth Factor Receptor (EGFR) mutations have emerged as the strongest predictor of response to EGFR-tyrosine kinase inhibitors mainly in patients with adenocarcinoma. Several EGFR mutation detection techniques are available, having both sensitivity and specificity issues, being the Sanger sequencing technique the reference standard, with the limitation of a relatively high amount of mutated cells needed for the analysis.
A novel nucleotide dispensation order for pyrosequencing was established allowing the identification and characterization of EGFR mutation not definable with commercially and clinically approved kits, and validated in a consecutive series of 321 lung cancer patients (246 biopsies or cytology samples and 75 surgical specimens).
61/321 (19%) mutated cases were detected, 17 (27.9%) in exon 21 and 44 (72.1%) in exon 19, these latter corresponding to 32/44 (72.7%) classical and 12/44 (27.3%) uncommon mutations. Furthermore, a novel, never reported, point mutation, was found, which determined a premature stop codon in the aminoacidic sequence that resulted in a truncated protein in the tyrosine kinase domain, thus impairing the inhibitory effect of specific therapy.
The novel dispensation order allows to detect and characterize both classical and uncommon EGFR mutations. Although several phase III studies in genotypically defined groups of patients are already available, further prospective studies assessing the role of uncommon EGFR mutations are warranted.