Effects of small extracellular vesicles isolated from pleural effusion on lung cancer cell proliferation and migration

Pleural effusion (PE) is a common clinical manifestation associated with advanced stages of both malignant and non-malignant diseases. PE frequently occurs in advanced non-small cell lung cancer (NSCLC) and contributes to tumor progression. NSCLC accounts for more than 85% of the lung cancers and remains a problem worldwide due to its late diagnosis and low rate of response to treatment. Extracellular vesicles (EVs) present in PE are emerging as key mediators of intercellular communication, capable of transferring oncogenic signals through their molecular cargo. Among these molecules, microRNAs (miRNAs) are increasingly recognized as important drivers of cancer progression. miR-21 is a representative onco-miRNA, involved in lung cancer progression; moreover EV-miR-21 upregulation at the pre-dissemination stage promotes cancer cell survival in the pleural cavity. This study compares, for the first time, the functional role of EVs isolated from malignant PE in NSCLC patients (NSCLC-PE-EVs) with those isolated from PE in patients with congestive heart failure (CHF-PE-EVs), focusing on their ability to modulate lung cancer cell behavior. The effects of these EVs were evaluated on COLO699 lung adenocarcinoma cells with proliferation, migration, and gene expression assays. NSCLC-PE was found to contain approximately twice the amount of EVs compared to CHF-PE. NSCLC-PE-EVs were enriched in the oncogenic miR-21-5p, while CHF-PE-EVs had higher levels of the tumor-suppressive miR-126-3p. Only NSCLC-PE-EVs induced dose-dependent increases in COLO699 cell proliferation and migration, consistent with elevated miR-21-5p expression. Functional studies confirmed that miR-21-5p mediates these effects by downregulating PTEN and PDCD4, and by upregulating MMP9 expression. Our findings show that NSCLC-PE-EVs promote malignant phenotypes in lung cancer cells via the transfer of miR-21-5p.