Narciclasine as a potential therapeutic agent to overcome EGFR-TKI resistance in non-small cell lung cancer.

backgroundNon-small cell lung cancer (NSCLC) is associated with abnormal activation of the epidermal growth factor receptor (EGFR) due to overexpression or mutations. While EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib, are used to treat NSCLC, resistance often develops, due to additional EGFR mutations or activation of alternative signaling pathways. Therefore, novel drugs to overcome EGFR-TKI resistance are needed for effective treatment of NSCLC. Narciclasin (Ncs) is a cytotoxic alkaloid from Narcissus species and exhibit antitumor and anti-inflammatory activities.

methodsCell viability assay was assessed using trypan blue staining and the Live/Dead viability assay. The growth inhibitory effects of Ncs were evaluated by WST-1 assay and cell cycle analysis across multiple NSCLC cell lines, including expressing A549 and H1299 (wt-EGFR), gefitinib-resistant H1975 (L858R/T790M-EGFR), gefitinib-sensitive PC-9 (exon 19 deleted-EGFR), and gefitinib-resistant PC-9 derivative, PC-9-GR. Ncs binding to wt-EGFR and mutant EGFRs was simulated with molecular docking models. Ncs effects on EGFR kinase activity was evaluated in vitro kinase assay using wt-EGFR and L858R/T790M-EGFR. Anti-tumor effects of Ncs in vivo were assessed using C. elegans tumor model expressing L858R/T790M-EGFR and mouse model xenografted with A549 and H1975. Histological analysis was conducted to measure EGFR, p-EGFR, and p-STAT3 levels in tumor tissues.

resultsNcs exhibited significant growth inhibitory effects on various NSCLC cell lines, including, A549, H1299 and PC-9 cells (gefitinib-sensitive), and H1975 and PC-9-GR cells (gefitinib-resistant). Notably, Ncs dramatically reduced cell growth with IC50 of 22 nM in H1975 cells expressing gefitinib -resistant EGFR mutant, much lower than any other cell lines. Ncs dramatically induced G2/M arrest in H1975 cells. Ncs binds to both wt-EGFR and mutant EGFRs in molecular docking models and preferentially inhibited the kinase activity of L858R/T790M-EGFR compared to wt-EGFR. In a C. elegans tumor model, Ncs reduced the tumor-mimicking multivulva phenotype. Ncs treatment resulted in decreased tumor growth in mice xenografted with A549 and H1975 cells and lowered levels of EGFR, p-EGFR, and p-STAT3 in tumor tissues.

conclusionsOur results suggest that Ncs exerts anti-tumor activity by inhibiting EGFR activity and downstream signaling. This effect is particularly evident in cases with EGFR mutations that confer resistance to TKIs, including gefitinib, supporting the potential of Ncs as a therapeutic agent for TKI-resistant NSCLC.