Liquid biopsy using circulating miRNAs for the identification of recurrence-associated biomarkers in glioblastoma CNS WHO grade 4

Abstract

Glioblastoma CNS WHO Grade 4 (GBM) is associated with poor prognosis and high recurrence rates despite the current therapeutic approaches. Conventional imaging, in particular Magnetic Resonance Imaging (MRI), is primarily used during follow-up to detect tumor recurrence but has limited ability to distinguish recurrence from therapy-related changes, such as tissue necrosis and postoperative scar tissue. Liquid biopsy using circulating tumor-specific serological biomarkers, such as miRNAs, provides a gene expression signature for early identification of GBM recurrence. This pilot “proof-of-concept” study investigated the potential of circulating tumor-derived miRNA in whole blood samples for early detection of tumor recurrence. In a previous whole-transcriptome screening (NGS) study, whole-blood samples (n = 33) from seven patients and tumor biopsies (n = 4) were used to identify biomarkers. Corresponding to tumor surgery and recurrence, miRNA expression was examined in pre-surgical blood samples and tumor tissues. In whole blood, we investigated whether a pattern could be identified indicating post-surgery downregulation, consistent with reduced tumor burden, followed by a return to pre-surgery levels at recurrence. We identified 1–19 miRNA species per patient (a total of 72 miRNAs) showing this pattern. In this manuscript, we present the qRT-PCR validation results. The 45 most promising miRNAs identified by NGS study were selected and quantified using qRT-PCR. In addition, miR-21 was included as a promising candidate reported in the literature. To address challenges in miRNA normalization, five normalization strategies and unnormalized raw Ct values were compared. Two normalization approaches (median DCt normalization and unnormalized raw Ct values) showed no systematic bias. Depending on the normalization method, the agreement between NGS and qRT-PCR ranged from 23.6 to 27.9%. Although the concordance between NGS and qRT-PCR was low at the individual-patient level, qRT-PCR identified a common set of 24 miRNAs differentially regulated across patients. Notably, miR-424-3p and miR-362-5p were shared by five of seven patients, followed by miR-1307-3p and miR-22-5p , each shared by four patients. Interestingly, miR-21 did not show the predefined recurrence-associated pattern in any patient. Blood-based miRNA profiling may complement imaging in longitudinal monitoring of GBM patients, although clinical benefits have not been confirmed, and validation in a larger independent cohort is required.