Cudratricusxanthone A Exhibits Antitumor Activities Against NSCLC Harboring EGFR L792H and G796R Triple Mutations via Regulating EGFR-ERK/AKT/STAT3 Signaling

Background: Acquired resistance to the third-generation EGFR tyrosine kinase inhibitor osimertinib, often mediated by EGFR triple mutations, poses a major clinical challenge in non-small cell lung cancer (NSCLC) treatment. Among these, some rare mutations, such as L858R/T790M/L792H and L858R/T790M/G796R, create steric hindrance that directly interferes with osimertinib binding, yet effective targeted therapeutic strategies for these specific mutations remain lacking. Cudratricusxanthone A (CTXA), a natural xanthone derivative isolated from Cudrania tricuspidata Bur., has demonstrated various pharmacological activities, but its effects against EGFR triple-mutant NSCLC have not been systematically investigated. Methods: Stable Ba/F3 and NIH/3T3 cell lines expressing EGFR L858R/T790M/L792H or L858R/T790M/G796R triple mutations were generated via electroporation. The antiproliferative effects of CTXA were evaluated by MTT/MTS assays, colony formation, and wound healing assays. Cell cycle distribution and apoptosis were analyzed by flow cytometry. Protein expression of EGFR signaling pathway components (p-EGFR, p-ERK, p-AKT, p-STAT3) and cell cycle regulators (Cyclin D1, CDK4) were examined by Western blotting. Molecular docking and 200 ns molecular dynamics simulations were performed to investigate the stability and binding modes of CTXA to the mutant EGFR kinase domains. Results: The successfully established triple-mutant cell lines exhibited high EGFR expression, IL-3-independent growth, and significant resistance to osimertinib. CTXA inhibited the proliferation of all triple-mutant cell lines in a time- and concentration-dependent manner, with 48 h IC50 values ranging from 0.362 to 2.488 μM. Mechanistically, CTXA suppressed EGFR autophosphorylation and downregulated downstream p-ERK, p-AKT, and p-STAT3. CTXA induced G1 phase cell cycle arrest by downregulating Cyclin D1 and CDK4, significantly promoted apoptosis, and inhibited cell migration. Molecular docking revealed that while osimertinib binding was blocked by steric hindrance from His-792 or Arg-796, CTXA adapted to the mutated ATP-binding pockets through multiple hydrogen bonds and extensive hydrophobic interactions. Molecular dynamics simulations confirmed the stable binding of CTXA to both mutant EGFR proteins over the 200 ns simulations. Conclusions: This study demonstrates for the first time that the natural compound CTXA possesses antitumor efficacy against EGFR L858R/T790M/L792H and L858R/T790M/G796R mutants by regulating EGFR-ERK/AKT/STAT3 signaling. Our findings position CTXA as a promising lead compound for tackling this challenging form of acquired resistance and highlight the value of natural products in multi-target antitumor drug discovery.