Unravelling Paclitaxel Resistance in Gastric Cancer: The Role of Small Extracellular Vesicles in Epithelial Mesenchymal Transition and Extracellular Matrix Remodelling.

Gastric cancer (GC) is a highly aggressive disease often complicated by resistance to chemotherapy agents like paclitaxel (PTX), which targets microtubules to induce apoptosis. Resistance arises through complex molecular mechanisms, including the overexpression of pro-angiogenic factors (VEGFA, ANG-2), activation of survival pathways (PDGFRβ, PPARγ), and epithelial-mesenchymal transition (EMT) driven by proteins such as VIM, E-CAD, N-CAD, and FLOT-1. The extracellular matrix (ECM), regulated by COL1A1 and influenced by PPARγ, acts as a physical barrier to drug penetration. Small extracellular vesicles (sEVs) have emerged as critical mediators of intercellular communication and may influence these resistance pathways. This study investigated the role of sEVs isolated from metastatic GC patients treated with Ramucirumab and PTX. Patients were stratified by progression-free survival (PFS) into rapidly progressing (RP) and controlled disease (CD) groups. sEVs from these patients were applied to HCEC-1CT and HEPA-RG cell lines. Cell viability assays, gene and protein expression analyses, and bioinformatic studies were conducted to assess the impact of sEVs on resistance-related markers. Results showed that sEVs from CD patients reduced the expression of markers associated with drug resistance, while sEVs from RP patients increased these markers, promoting angiogenesis, EMT, and ECM remodeling. These changes correlated with enhanced cell survival and resistance phenotypes. Bioinformatic analyses confirmed that sEVs modulate inflammation, ECM dynamics, and EMT pathways. In conclusion, sEVs from metastatic GC patients significantly influence chemoresistance and tumor progression. Targeting sEV-mediated signaling may offer novel therapeutic strategies to overcome resistance and improve treatment outcomes in gastric cancer.