3MO - Beyond the expected: Circulating tumor cells in glioblastoma reveal hidden heterogeneity and become potential diagnostic biomarkers

Background

The detection of circulating tumor cells (CTCs) in the blood of glioblastoma (GBM) patients provides a non-invasive method for assessing tumor-related information. Our aim is to use GBM CTCs to obtain knowledge about the tumor and improve the current GBM diagnosis and prognosis.

Methods

Blood samples were collected from 20 primary tumor cases, 18 recurrences, 10 healthy controls, and 4 unhealthy controls. CTCs were isolated using the Parsortix Cell Separation System and the DEPArray system. CTCs were counted in all samples. Copy Number Alterations (CNAs) analysis was performed on some isolated CTCs. Single-cell RNA sequencing (scRNAseq) was also conducted on a primary cancer cell line from a GBM tumor, with CNAs analyzed across all cell populations.

Results

CTC counts were significantly higher in both primary and recurrent GBM patients compared to healthy controls (average CTCs: 10.2 vs.3.1). Primary GBM cases had more CTCs than recurrent cases, with averages of 15 and 4.8, respectively. Based on these findings, a cut-off of 5 CTCs was established to identify tumor samples. Among the four special cases studied, which included lymphoma, radionecrosis, oligodendroglioma, and xanthoastrocytoma, this cut-off validated the accuracy of our CTC detection method. CNA analysis revealed that 51% of isolated CTCs exhibited alterations, while 49% were wild-type. This novel finding was corroborated by scRNAseq analysis of the GBM primary cancer cell line analyzed, wherein both wild-type cells and CNAs were observed with a percentage of CNAs of 51% and 49% respectively, mirroring the distibution observed in CTCs.

Conclusions

Our study demonstrates the potential of CTCs as a non-invasive diagnostic tool for GBM. Elevated CTC counts, especially in primary GBM, highlight their use as biomarkers for disease progression. Additionally, the discovery of wild-type CTCs underscores the heterogeneity within CTC populations, reflecting the diverse structure of GBM itself.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.