Expression Analysis of let-7a-5p and miR-21-3p in Extracellular Vesicles Derived from Serum of NSCLC Patients

Background/Objectives: Despite the significant advancements made in the diagnosis of lung cancer, the traditional diagnostic methods remain limited because they are often invasive, expensive, and not suitable for regular screening, creating a need for more accessible and non-invasive alternatives. In this context, the analysis of miRNAs in EVs and free circulating microRNA may be used as liquid biopsies in lung cancer to identify individuals at risk. This study aimed to compare miRNA profiles in the serum and EVs derived from lung cancer patients by focusing on Let-7a-5p and miR-21-3p. Materials and Methods: Serum and EVs were isolated from lung cancer patients and healthy controls. EVs were characterized using nanoparticle tracking analysis, electron microscopy, and Western blotting for surface markers (CD63, CD81, TSG101). Total miRNA levels were quantified in the serum and EVs, and specific miRNAs (hsa-let-7a-5p and hsa-miR-21-3p) were analyzed using RT-qPCR. Statistical analysis evaluated miRNA expression across clinicopathological features, including age, gender, smoking status, tumor stage, cancer type, and EGFR mutation status. Results: Total miRNA levels were significantly enriched in EVs compared to the serum. Let-7a-5p was downregulated in EVs from patients with advanced-stage lung cancer (Stage III-IV) compared to those with early-stage cancer and controls (p < 0.05), while no differences were observed in the serum. Conversely, miR-21-3p was significantly upregulated in EVs and serum from advanced-stage patients (p < 0.01) and in adenocarcinoma compared to squamous cell carcinoma (p < 0.05). No significant differences were observed for age, gender, or smoking status. Conclusions: Our findings highlight the differential expression of miRNAs in EVs and the serum, emphasizing the diagnostic potential of EV-associated Let-7a-5p and miR-21-3p in lung cancer. These results suggest that EVs are a more robust source for miRNA biomarkers compared to the serum.