Mitochondrial DNA content in tumor tissue and blood of patients with glioblastoma 一 A reliable biomarker?

摘要

Introduction: Recent studies have shown that mitochondrial DNA (mtDNA) content in the tumor tissue is associated with patient survival in glioblastoma (GBM). However, mtDNA content in the blood of patients with GBM and its variation during treatment has not been documented. Hence, we assessed mtDNA content in blood and tumor tissue of GBM patients, its association with survival, and the variation of mtDNA content in blood with treatment. Materials and Methods: GBM tissue obtained from 20 patients, 2 ml blood collected from the same patients at the time of presentation and following radiation therapy (RT), 2 ml blood obtained from 20 healthy volunteers were assessed for mtDNA content using quantitative real-time polymerase chain reaction (comparative ct method). The mtDNA content is expressed as the mtDNA/nuclear gene ratio. Results: The mean mtDNA copy number in the GBM tissue was 492.3819, while in the blood of patients, it was 41.76 ± 19.45. In healthy volunteers1 blood, it was 55.97 ± 5.78 (P = 0.04). The median overall survival was 13 months in patients with high tumor mtDNA content and 10 months in patients with low tumor mtDNA content (P = 0.04). Patients with low-mtDNA content in the blood had a relatively higher content in the tumor tissue (correlation coefficient — 0.26； P = 0.27). No significant difference was noted between mtDNA content in preoperative blood (41.76 ± 19.45) and post-RT blood sample (44.16 ± 12.83) (P = 0.6). Conclusion: High GBM tumor mtDNA copy number is associated with better overall survival. mtDNA content in the blood is lower in GBM patients when compared with healthy volunteers. mtDNA content in the blood of the patients did not vary following surgery and RT