P2.01-52 Identification of Leptomeningeal Metastasis-Specific Exosomal miRNA Signatures in Cerebrospinal Fluids of NSCLC Patients

Leptomeningeal metastasis (LM) is a devastating complication with poor prognosis in non-small-cell lung cancer (NSCLC) patients. The confirmed diagnosis of LM usually involves neurological evaluation, MRI imaging, and cytopathology analysis of limited tumor cells from cerebrospinal fluid (CSF). Exosomes are extracellular vesicles in body fluids enriched with microRNAs (miRNAs), which have been implicated to participate in brain metastasis. Here, we aimed to identify LM-specific exosomal miRNA signatures in NSCLC patients to elucidate their potential role in LM mechanism and to predict LM via liquid biopsy. Exosomes prepared from CSF and plasma samples of 39 advanced NSCLC patients with (LM+) or without (LM-) LM as well as 12 non-cancer individuals (NC) were underwent small RNA next-generation sequencing. For patients in the LM+ group, paired plasma samples were taken before (PLM+pre) and upon (PLM+post) LM diagnosis. Exosomal miRNA profiles were subjected for differential expression analysis, pathway enrichment analysis, and signature discovery. Unsupervised hierarchical clustering of the miRNA expression profiles clearly separated CSF samples into LM+ and LM free groups (LM- and NC). Interestingly, these samples were stratified based on their LM status only, regardless of their intraparenchymal metastasis status. In total, 247 (185 up and 62 down-regulated) miRNAs were identified differentially presented in the LM+ CSF exosome samples compared to the LM- and NC groups. Top altered miRNAs include dramatically up-regulated miR-200 family and down-regulated miR-144/451 cluster. Predicted gene targets of these top-regulated miRNAs were significantly enriched in Ras/MAPK/PI3K-AKT signaling, endocytosis pathways, and so on. Promisingly, a signature of five CSF exosomal miRNAs (let-7e-5p, miR-28-3p, miR-375, miR-200a-3p, and miR-486-5p) was identified for classification of LM+ patients with 100% sensitivity and 100% specificity. Due to the higher background complexity, we only identified one miRNA (miR-24-3p) was significantly up-regulated and one miRNA (miR-92b-5p) was significantly down-regulated in LM+ patients’ plasma-derived exosomes (PLM+pre and PLM+post) compared with the LM free group (PLM- and PNC). However, a combined signature of seven miRNAs (miR-24-3p, miR-223-3p, miR-340-5p, miR-27a-3p, miR-423-5p, miR-2110 and miR-342-5p) from PLM+pre samples was identified for the prediction of future LM with 81% sensitivity and 76% specificity. NSCLC patients with LM present a remarkably distinct CSF exosomal miRNA signature, which may involve in the progression of LM, and can be used as diagnostic biomarkers for LM. Furthermore, the identification miRNA signature in the pre-LM plasma samples suggests the potential use of liquid biopsy to predict LM for better patient care.