Diagnosis of Glioma Tumors Using Circulating Cell-Free DNA

Introduction Gliomas are the most frequent brain tumors, making up about 30% of all brain and central nervous system tumors, and 80% of all malignant brain tumors. Existing standard diagnostic technique for glioma tumor... [ view full abstract ]

Introduction

Gliomas are the most frequent brain tumors, making up about 30% of all brain and central nervous system tumors, and 80% of all malignant brain tumors. Existing standard diagnostic technique for glioma tumor includes tissue biopsy, which is a highly invasive and hence a risky technique for the patient’s survival. ‘Liquid biopsy’ is a new and recently developed non-invasive cancer diagnostic technique, which includes use of circulating cell-free DNA (cfDNA) fragments for tracing tumor markers. CfDNA fragments are one of those molecular bits that are released into the bloodstream after rapid apoptosis or necrosis of the tumor cells in the cancer patients.

Our goal is to do comprehensive study between distinct types of glioma cancer tumors and cfDNA of the respective patients, to elucidate the scope of cfDNA in liquid biopsy technique for glioma diagnosis.

Methods

We collected 8 different glioma patient’s tumor tissue and plasma samples and then isolated tumor DNA from glioma tumor tissue and circulating cell-free DNA(cfDNA) from the respective glioma patient’s plasma. Isolated tumor DNA and cfDNA then deeply sequenced on Illumina HiSeq 2500 and then NGS data was analyzed to find out single nucleotide variants (SNVs) as well as structural variants on both cfDNA and tumor gDNA.

Results

We have successfully detected glioma specific mutations such as IDH1, IDH2, PDGFRA, NOTCH1, PIK3R1 and TP53, from cfDNA isolated from the plasma of glioma patients and could relate this mutations to the different tumor grades of glioma. We are also studying the dynamics of these mutations in response to glioma drug treatment by collecting blood samples at different time intervals.

Discussion

This study may help in developing liquid biopsy technique for glioma tumor diagnosis and in its prognosis for monitoring the glioma treatment by non-invasive approach, and will eventually help physicians to decide the right treatment on appropriate time while bypassing the existing 'wait-and-see' approach of treatment monitoring.