Rosmarinic acid potentiates gefitinib in lung adenocarcinoma by modulating interactions between cancer cells and cancer-associated fibroblasts.

While cancer-associated fibroblasts (CAFs) significantly influence tumor progression, their temporal dynamics remain poorly understood. We investigated time-dependent interactions between non-small cell lung cancer (NSCLC) cells and CAFs, and evaluated rosmarinic acid (RA)'s potential to modulate these interactions. HCC827 lung adenocarcinoma cells and MRC-5 fibroblasts were co-cultured in vitro. CAF activation markers (α-SMA, FAP) and epithelial-mesenchymal transition (EMT) were assessed through morphological and molecular analyses. Xenograft models with different tumor-to-fibroblast ratios (1:1, 1:2) evaluated tumor growth dynamics and RA's therapeutic effects combined with gefitinib. Time-course analysis revealed a biphasic pattern in tumor-CAF interactions. CAF activation markers reached peak levels by day 6, followed by maximal EMT marker expression in NSCLC cells at day 8. In xenograft models, higher CAF proportions initially inhibited tumor growth but accelerated tumor progression. RA treatment significantly attenuated CAF activation markers and reversed EMT-related changes in cancer cells, leading to reduced tumor growth in CAF-enriched xenografts. The combination of RA with gefitinib demonstrated enhanced anti-tumor effects compared to gefitinib alone. CAFs exhibit temporally biphasic roles in NSCLC progression characterized by initial suppression followed by promotion of tumor microenvironment deterioration. RA effectively modulates these tumor-stromal interactions, enhances gefitinib efficacy, and delays the development of drug resistance.