Origins of Glioblastoma: Initiation and Molecular Signatures of Extreme Aggressiveness

Compared with other malignancies, brain tumors rank among the most fatal types of cancer affecting humans, with the lowest survival rates. The overall 5-year survival rate for all primary brain tumors is approximately 5%, although this figure varies significantly on the basis of factors such as tumor type, location, size, patient age, and overall health. Glioblastoma, in particular, is among the most aggressive lethal cancers, making it one of the most devastating brain tumors. Its molecular pathogenesis is highly complex and involves genetic mutations in key regulatory genes, such as IDH1/2, EGFR, PDGFRA, the hTERT promoter, and NF1, along with epigenetic alterations and contributions from the tumor microenvironment, all of which drive tumor progression and invasion. Addressing the extremely poor survival rate of glioblastoma requires a deeper understanding of its origins and the cells responsible for its initiation. Various cancer initiation theories—such as the two-hit hypothesis, random mutation model, and clonal selection hypothesis—have proven experimentally effective in explaining its development. However, the cancer stem cell hypothesis stands out, as it successfully accounts for glioblastoma’s unmanageable aggressiveness and recurrence. Glioblastoma cancer stem cells (GSCs) can self-renew, differentiate into multiple tumor cell types, resist conventional therapies, and contribute to tumor heterogeneity, metastasis, and infiltration into surrounding brain tissue. These characteristics significantly impact patient prognosis and mortality. The exact cellular origin of glioblastoma remains a subject of ongoing research. However, studies suggest that glioblastoma may arise from neural stem cells (NSCs) or glial precursor cells, which undergo oncogenic mutations that drive uncontrolled proliferation. The molecular subtype of a tumor is often influenced by the lineage of its originating cells, with mesenchymal stromal cells emerging as potential glioblastoma-initiating cells, particularly in tumors with mesenchymal molecular features.