Tumor-intrinsic TLR4 signaling as a context-dependent rheostat in glioblastoma

Glioblastoma (GBM) remains resistant to therapy due to cellular heterogeneity and adaptive stress responses, yet the role of tumor-intrinsic Toll-like receptor 4 (TLR4) signaling in this process remains unresolved. This review addresses a central inconsistency in the field by defining tumor-intrinsic TLR4 as a context-dependent signaling rheostat that generates distinct biological outcomes rather than a uniform tumor-promoting pathway. Across experimental systems, TLR4 signaling produces divergent effects that range from mesenchymal transition, invasion, and adaptive survival under chronic or therapy-associated conditions, to differentiation, apoptosis, and increased treatment sensitivity under specific cellular and temporal contexts. These opposing outputs are not contradictory but arise from defined determinants, including ligand environment, signaling dynamics, tumor cell state, and metabolic conditions. This framework explains previously discordant findings and establishes that the functional role of tumor-intrinsic TLR4 cannot be inferred from receptor activation alone. Instead, its impact is conditional and state-dependent. This perspective defines a clear experimental and translational priority: to identify the contexts in which tumor-intrinsic TLR4 signaling sustains tumor persistence versus exposes therapeutic vulnerability, thereby enabling rational and stratified intervention strategies in GBM.