Frequency of cis and trans EGFR T790M and activation mutations in tumors treated with EGFR inhibitors

• Published in: Journal of Iwate Medical Assiociation Vol. 72; no. 2; pp. 47 - 58
• Main Authors: Hirano, Kunio, Sugai, Mayu, Terasaki, Hiroshi, Chiba, Ryosuke, Maemondo, Makoto, Watanabe, Kana, Fukuhara, Tatsuro, Sato, Hideomi, Akiyama, Masachika, Nagashima, Hiromi
• Format: Journal Article
• Language: English
• Published: Iwate Medical Association 01.06.2020
• Subjects: allele frequency; cis configuration; EGFR gene mutation; osimertinib; trans configuration
• ISSN: 0021-3284; 2434-0855
• DOI: 10.24750/iwateishi.72.2_47

The exon 20 T790M mutation confers resistance to 1st- and 2nd-generation EGFR-TKIs while the C797S mutation confers resistance to the 3rd-generation EGFR-TKI, osimertinib. The presence of C797S in trans with T790M restores sensitivity to 1st/2nd-generation EGFR-TKIs. In the current study, we analyzed whether the T790M mutation was present in cis or trans with activating mutations in tumors treated with osimertinib.We analyzed tissue specimens harboring both T790M and activating mutations in patients with non-small cell lung cancer obtained from May 2016 to June 2018. After the presence of EGFR mutation was confirmed using the PNA-LNA PCR clamp method, we determined whether activating mutations were located in cis or trans with the T790M mutation using RT-PCR. Results were validated using colony PCR followed by Sanger sequencing, which allowed us to calculate the allele frequency of each. Both EGFR mutations were detected in 11 out of 23 cases. All 11 cases had cis configuration. The low allele frequency of T790M might be related to the short duration of osimertinib treatment.The cis configuration of T790M and activating mutations in all specimens was confirmed, and this result was in contrast to the existence of trans configuration of C797S and T790M.