24 25 26 2 SUMMARY 27Genome-wide DNA methylation profiling has shown that epigenetic abnormalities are 28 biologically important in glioma and can be used to classify these tumors into distinct prognostic 29 groups. Thus far, DNA profiling has required surgically resected glioma tissue; however, 30 gliomas release tumoral material into biofluids, such as blood and cerebrospinal fluid, providing 31 an opportunity for a minimally invasive testing. While prior studies have shown that genetic and 32 epigenetic markers can be detected in blood or cerebrospinal fluid (e.g., liquid biopsy [LB]), 33 there has been low sensitivity for tumor-specific markers. We hypothesize that the low 34 sensitivity is due to the targeted assay methods. Therefore, we profiled the genome-wide CpG 35 methylation levels in DNA of tumor tissue and cell-free DNA in serum of glioma patients, to 36 identify non-invasive epigenetic LB (eLB) markers in the serum that reflect the characteristics of 37 the tumor tissue. From the epigenetic profiles of serum from patients diagnosed with glioma 38 (N=15 IDH mutant and N=7 IDH wildtype) and with epilepsy (N=3), we defined glioma-specific 39 and IDH-specific eLB signatures (Glioma-eLB and IDH-eLB, respectively). The epigenetic 40 profiles of the matched tissue demonstrate that these eLB signatures reflected the signature of the 41 tumor. Through cross-validation we show that Glioma-eLB can accurately predict a patient's 42 glioma from those with other neoplasias (N=6 Colon; N=14 Pituitary; N=3 Breast; N=4 Lung), 43 non-neoplastic immunological conditions (N=22 sepsis; N=9 pancreatic islet transplantation), 44 and from healthy individuals (sensitivity: 98%; specificity: 99%). Finally, IDH-eLB includes 45 promoter methylated markers associated with genes known to be involved in glioma 46 tumorigenesis (PVT1 and CXCR6). The application of the non-invasive eLB signature discovered 47 109 with glioma. We showed that the eLB could differentiate glioma from non-tumoral brain tissue 110 and stratify gliomas based on prognostic class (e.g., IDH mutation status). We further observed 111 that the specificity of the eLB allowed accurate discrimination of patients with glioma from 112 patients with tumors of other origins and from patients with immune-related disease states 113 (pancreatic islet transplantation and sepsis). The IDH-eLB signature includes promoter 114 methylated markers associated with genes known to be involved in glioma tumorigenesis (e.g.,
115PVT1 and CXCR6). Finally, we propose a novel clinical approach to apply the eLB panels to 116 complement the standard of care in the diagnosis and follow-up. The ability to monitor patients 117 6 by eLB has the potential to improve the pre-and post-surgical quality of care for patients 118 harboring gliomas.
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RESULTS
120Glioma cell-free DNA methylome 121 In this study, we selected 22 matching pairs of primary glioma tissue and serum, stored at the 122 Hermelin Brain Tumor Center (HBTC) bank from patients who underwent neurosurgery at the 123 Henr...