What is exon 21 mutation?

What is exon 21 mutation?

Mutations of epithelial growth factor receptor (EGFR) in exon 19 and 21 are both believed to be associated with carcinogenesis, sensitivity to tyrosine kinase drugs and with the prognosis of non-small cell lung cancers (NSCLCs). However, their exact clinical significance remains disputable.

Is T790M an exon 20 mutation?

The secondary mutation in exon 20, T790M, detected in approximately 50% of re-biopsy samples after TKI therapy, is regarded as the most common cause of acquired resistance to TKIs (6).

What is L858R mutation?

The EGFR L858R mutation arises from the nucleotide change c. 2573T>G in exon 21, resulting in an amino acid substitution of the leucine (L) at position 858 by an arginine (R). Genetic alterations in the gene encoding EGFR have been found in lung cancers.

What is exon 20 S768I?

S768I mutation in exon 20 of the EGFR gene is a rare mutation that has been identified sporadically in previous studies and is reported to confer reduced sensitivity to gefitinib in vitro compared with the two most commonly observed types of mutations: Exon 19 deletions and p.

Which exon is T790M?

A second mutational event in EGFR, the T790M substitution in exon 20, is thought to account for more than half of all cases of acquired resistance to first-generation EGFR inhibitors in NSCLC.

Where is the L858R mutation found?

The L858R substitution is the single most common mutation (approximately 40% of all mutations), and it lies in the activation loop (A-loop) of the kinase.

Which is the most common mutation in EGFR exon 21?

Sequist et al7 screened 98 patients from eleven centers and concluded that exon 19 deletions and the exon 21 point mutation L858R accounted for 53% and 26% of the mutations, respectively. The remaining 21% atypical mutations included T790M in exon 20, G719A in exon 18, and L861Q in exon 21.

Can a point mutation cause an aberrant transcript?

Point mutations at these consensus sequences can cause improper exon and intron recognition and may result in the formation of an aberrant transcript of the mutated gene.

How are mutations related to pre mRNA splicing?

Precise pre-mRNA splicing, essential for appropriate protein translation, depends on the presence of consensus “cis” sequences that define exon-intron boundaries and regulatory sequences recognized by splicing machinery. Point mutations at these consensus sequences can cause improper exon and intron …