AIMS: Glioblastoma (GBM), particularly mesenchymal and recurrent GBM, often develops resistance to temozolomide (TMZ) and is characterized by extensive infiltration of monocyte-derived macrophages (MDM), which contributes to treatment failure. However, the mechanisms through which TMZ-resistant GBM recruits MDM remain poorly understood. This study aims to investigate the molecular drivers of MDM infiltration in the context of TMZ resistance and to identify potential therapeutic targets to disrupt this process.
METHODS: Patient-derived GBM organoid (GBO) was utilized as a model system. We performed molecular profiling to identify genes upregulated in TMZ-resistant recurrent GBO. Endothelial cells (ECs) cultures and preclinical GBM models were used to examine disruption of tight junctions and monocyte infiltration. Mechanistic studies employed genetic knockdown, pharmacological inhibition, and assays, including Chromatin immunoprecipitation-quantitative PCR, Western blot, and immunostaining, to validate pathway activity and protein interactions.
RESULTS: COL6A1 (Collagen type VI alpha 1 chain) was significantly upregulated in TMZ-resistant recurrent GBO and associated with poor survival. COL6A1 is bound to ITGB1 (Integrin beta-1) on ECs, leading to disruption of tight junctions via UBD (Ubiquitin-like modifier D)-mediated degradation of claudin-5. Furthermore, COL6A1 activated the FAK/SRC/Hippo/YAP signaling axis, which promoted lactylation of the transcription factor IKZF1 (IKAROS family zinc finger 1) at lysine 255. Lactylated IKZF1 translocated to the nucleus and recruited the chromatin remodeler Chromodomain-helicase-DNA-binding protein 1 to enhance UBD transcription, thereby promoting endothelial barrier breakdown and monocyte infiltration. Treatment with lenalidomide (LEN), an IKZF1 inhibitor, restored claudin-5 expression, reduced MDM accumulation, and re-sensitized TMZ-resistant tumors to chemotherapy in preclinical models.
CONCLUSION: This study identifies a novel signaling cascade whereby TMZ-resistant GBM secretes COL6A1 to activate an IKZF1-UBD axis in ECs, disrupting blood vessel integrity and facilitating MDM infiltration. Our findings delineate the pivotal mechanism by which tumor cells engage ECs to drive MDM infiltration - a linchpin part of the positive-feedback loop that couples TMZ resistance to MDM influx. Targeting IKZF1 with LEN represents a promising strategy for restoring endothelial barrier function, reducing MDM infiltration, and enhancing chemosensitivity in GBM.
