Synergistic Enhancement of Osimertinib Efficacy in Non-small Cell Lung Cancer Cells Through Epigallocatechin-3-Gallate: Mechanistic Insights Into YAP/TEAD/CTGF Axis Inhibition.

Purpose: Combinatorial therapies are essential for treating advanced non-small cell lung cancer (NSCLC), particularly overcoming resistance to third-generation epidermal growth factor receptor (EGFR) like osimertinib (OSI). The Hippo signaling pathway, a critical regulator of cell proliferation, apoptosis, and tumor progression, is often dysregulated in NSCLC and contributes to chemo-resistance. This study investigated the potential of epigallocatechin-3-gallate (EGCG), a green tea polyphenol, to overcome OSI resistance by modulating the Hippo signaling pathway, specifically through inhibition of the YAP-1 (Yes-associated protein)-TEAD (TEA domain transcription factor)-CTGF (connective tissue growth factor) axis.

Methods: Using stepwise dose escalation, OSI-resistant (OR) clones were developed from EGFR T790M-mutated H460 cells. The anti-proliferative effects of EGCG were assessed, and synergistic interactions between OSI and EGCG were analysed using combination index (CI) values and the median effect concept. Mechanistic studies evaluated the co-treatment's impact on the Hippo signaling pathway, focusing on the inhibition of the YAP/TEAD/CTGF signaling axis.

Results: The OR clones exhibited significantly higher IC₅₀ values for OSI (25.12-28.48 µM) compared to parental H460 cells (2.74±0.2µM). EGCG treatment reduced cell viability in a concentration-dependent manner, with IC₅₀ values of 102.54±0.23μM for H460 cells and 225.79-237.36 µM for OR clones. Combination treatment of OSI and EGCG showed strong synergy at a 1:2 molar ratio, with CI values indicating synergism across a range from IC₅₀ to IC₉₅. Mechanistically, co-treatment suppressed the overexpression of the YAP/TEAD/CTGF axis, restoring Hippo pathway activity and reversing OSI resistance.

Conclusion: This study provides evidence that EGCG effectively targets the Hippo signaling pathway to overcome OSI resistance in NSCLC. The inclusion of EGCG in combinatorial therapies holds promise as a novel approach to combat therapeutic resistance and improve outcomes for patients with EGFR-mutated NSCLC.