Sensitivity analysis of EGFR L861Q mutation to six tyrosine kinase inhibitors

Lung cancer is one of the most common carcinomas with the highest mortality in the world. Non-small cell lung carcinoma has a large proportion of epidermal growth factor receptor (EGFR) mutations, of which rare EGFR mutations account for about 10%-20%. Currently, tyrosine kinase inhibitors (TKIs) therapy is a standard treatment for patients with non-small cell lung carcinoma with EGFR mutations. To date, the toxicological effects of the EGFR L861Q variant (less than 2%) have been rarely reported, so further investigation of its sensitivity to six first-in-class TKIs is of great clinical interest.

In this study, two EGFR L861Q variants cell lines (EGFR L861Q variant and EGFR L861Q + exon 19 deletion variant) were established by CRISPR-Cas9 gene-editing technology. The steady-state plasma concentrations of six TKIs (gefitinib/erlotinib/icotinib, the first generation; dacomitinib/afatinib, the second generation; and osimertinib, the third generation) were tested, respectively. The change of cell viability, proliferation, cloning ability, mitochondrial membrane potential and apoptosis were detected by MTT assay, EdU staining assay, colony formation assay, mitochondrial membrane potential and apoptosis test. TUNEL and Annexin V / PI staining were used to detect cell apoptosis, and flow cytometry was employed to explore the sensitivity of two variants to six TKIs.

Our study indicated that the six TKIs inhibited the viability of the two cell lines in a time-dependent manner, and the inhibitory time of six TKIs on proliferation was different between the two cell lines. The proliferation and cloning ability of two cell lines were inhibited by six TKIs. The cytoskeleton morphology, microfilament structure and distribution of the two cell lines were changed by six TKIs. Compared with the control, the mitochondrial membrane potential decreased while the apoptosis increased of the two of variants after treatment with the six TKIs, and the associated mechanisms were elucidated.

Based on the above results, EGFR L861Q + 19del variant and EGFR L861Q variant showed significant sensitivity to six first-in-class TKIs. Among the six TKIs, the first generation TKIs (gefitinib/erlotinib/icotinib), showed stronger inhibition ability to the EGFR L861Q + 19del variant and EGFR L861Q variant, among which gefitinib showed the strongest inhibition.