Study of plasma exosomal miRNAs as novel biomarkers for differentiating primary central nervous system lymphoma and glioblastoma

Preoperative diagnosis of the nature of PCNSL is crucial for distinguishing it from commonly confused intracranial gliomas, such as glioblastoma multiforme (GBM). The present research aims to sequence peripheral blood exosomal miRNAs from PCNSL and GBM patients, and to identify the discriminative miRNAs with high feasibility. Plasma exosomal RNAs were extracted, and miRNA sequencing was performed. The miRNAs with significant differences were validated by RT-qPCR. A total of 67 miRNAs were significantly different between the PCNSL and GBM groups. Twenty-seven PCNSL and 27 GBM patients were enrolled for the RT-qPCR validation of 10 selected differentially expressed miRNAs. The expression levels of plasma exosomal hsa-miR-148a-3p, hsa-let-7f-5p, hsa-miR-345-5p and hsa-miR-4433b-5p were upregulated in the PCNSL group compared with those in the GBM group (P = 0.019, P = 0.036, P = 0.009, and P = 0.001, respectively). The combined panel comprising hsa-miR-148a-3p, hsa-miR-345-5p, and hsa-miR-4433b-5p demonstrated significantly enhanced diagnostic performance, with an area under the ROC curve (AUC) of 0.791. Immunohistochemistry analysis revealed that the expression level of EGFR in PCNSL was significantly lower than that in GBM. Western blot and RT-qPCR analysis of EGFR expression levels in LN229 cells revealed that miR-148a-3p and miR-4433b-5p downregulated EGFR expression. The results of luciferase reporter assay showed that the relative luciferase activity of HEK293T cells transfected with EGFR-WT was notably suppressed by miR-4433b-5p (P < 0.001). In conclusion, the plasma exosomal hsa-miR-148a-3p, hsa-miR-345-5p, and hsa-miR-4433b-5p might be identified as novel biomarkers for differentiating PCNSL and GBM. The increased expression level of EGFR in GBM may be achieved by the negative regulatory effects of miR-4433b-5p. The diagnostic performance of the miRNA biomarkers still needs to be further verified in larger sample size cohorts.