TMIC-26. Intercellular transfer of extrachromosomal DNA in glioblastoma

Abstract Glioblastoma (GBM) represent a complex ecosystem of intertwined interconnections between various cell types. Through diverse mechanisms of intercellular communication, GBM cells can modulate the behavior of both malignant and non-tumor cells, promoting cancer progression. One of the key drivers of GBM plasticity and adaptability is extrachromosomal DNA (ecDNA). ecDNA allows GBM cells to rapidly and reversibly modify their genome and by thousands of folds increase the expression of critical oncogenes. However, virtually nothing is known about the role of ecDNA in intercellular communication. Using qPCR and immunofluorescent staining combined with fluorescent in situ hybridization, we demonstrated that ecDNA can be transported between different populations of GBM cells via tumor microtubes in vitro. The efficiency of this transfer substantially differs for various ecDNAs and for GBM cells derived from different patients. Our results suggest that recipient GBM cells can maintain exogenous ecDNA for up to five weeks. Further experiments with iPSC-derived cerebral organoids implanted with ecDNA-containing GBM cells revealed ecDNA transfer between GBM and non-tumor cells. To confirm that this process occurs in patients, we performed single-cell RNA sequencing and whole-genome sequencing of malignant and adjacent non-transformed brain tissues. Integrated analysis of mutations in DNA and RNA, copy number variations, and gene expression patterns confirmed that a substantial fraction of non-cancer cells within the tumor microenvironment harbor ecDNA. We hypothesize that ecDNA transfer between GBM cells can accelerate cancer evolution by disseminating the most beneficial ecDNA molecules within the tumor, thereby bypassing the bottleneck of clonal competition. On the other hand, ecDNA transfer from GBM to non-tumor cells can theoretically have a profound impact on the properties of recipient normal cells, altering their phenotypes to promote further tumor progression or even turning them into seeds for tumor recurrence.