Expert consensus has defined minimum requirements for routine testing and identification of epidermal growth factor (EGFR) mutations (15% of tumors harbor EGFR exon 19 deletions or exon 21 L858R substitutions) and anaplastic lymphoma kinase (ALK) rearrangements (5% of tumors) in advanced lung adenocarcinomas (ACs).
Compared to those with classic activating EGFR mutations, lung adenocarcinomas with exon 20 insertion mutations were characterized by significantly younger age at diagnosis (P = 0.032 for exon 20 insertions vs. L858R) and shorter relapse-free survival [P = 0.045 for exon 20 insertions versus (vs) exon 19 deletions].
EGFR exon 20 insertion testing identifies a distinct subset of lung adenocarcinomas, accounting for at least 9% of all EGFR-mutated cases, representing the third most common type of EGFR mutation after exon 19 deletions and L858R.
We have used unbiased phosphoproteomic approaches, based on quantitative mass spectrometry using stable isotope labeling with amino acids in cell culture (SILAC), to identify tyrosine phosphorylated proteins in isogenic human bronchial epithelial cells (HBECs) and human lung adenocarcinoma cell lines, expressing either of the two mutant alleles of EGFR (L858R and Del E746-A750), or a mutant KRAS allele, which are common in human lung adenocarcinomas.
A previously unreported mutation in exon 21 of EGFR, which leads to substitution of alanine for threonine at position 854 (T854A), was identified in one patient with a drug-sensitive EGFR L858R-mutant lung adenocarcinoma after long-term treatment with tyrosine kinase inhibitors.