Serum Exosomal miRNA Might Be a Novel Liquid Biopsy to Identify Leptomeningeal Metastasis in Non-Small Cell Lung Cancer

PURPOSE: The survival time of patients with leptomeningeal metastasis (LM) of lung cancer is very short, and the clinical characteristics of LM are varied, making the clinical diagnosis difficult. At present, a positive CSF fluid (CSF) cytology result remains the gold standard for diagnosing LM in lung cancer; however, the process of collecting CSF is traumatic and far less convenient than blood collection. With the development in technology, an increasing number of studies prefer to use liquid biopsy to diagnose or predict the occurrence of the disease. Therefore, we aimed to explore whether serum exosomal miRNA can replace miRNA from CSF to identify or predict the occurrence of LM. PATIENTS AND METHODS: Herein, four pairs of serum and CSF samples were collected at four different time points from a patient with LM from non-small cell lung cancer (NSCLC). Serum and CSF exosomes were extracted. Western blot (CD63, TSG101) and electron microscope analyses were used to verify exosome extraction, after which exosomal miRNA sequencing was performed. Next, exosomal miRNA from serum and CSF samples from seven patients with LM and 30 patients without LM were collected for validation. RESULTS: Sequencing results of serum exosomal miRNA and CSF exosomal miRNA showed that there were 44 exosomal miRNAs stably co-expressed at four different time points. Then, three common miRNAs related to LM were found (hsa-miR-483-5p, hsa-miR-423-5p, and hsa-miR-342-5p). Subsequently, exosomal miRNA was extracted from serum and CSF samples from seven patients with LM and 30 patients without LM for verification, and the expression of these exosomal miRNA was detected. The results showed that miRNA-483-5p and miRNA-342-5p significantly differed in LM−/+ patients (P = 0.0142 and P = 0.0031, respectively), whereas miRNA-423-5p had no difference (P = 0.0921). Additionally, as the symptoms improved, the expression of these miRNAs decreased or remained stable. CONCLUSION: Serum exosomal miRNA (hsa-miR-483-5p, and hsa-miR-342-5p) may be involved in LM of lung cancer and may replace CSF to predict LM in NSCLC.