Exosomal Lnc-DLK1-35 reprograms microglia into a pro-tumorigenic phenotype via a non-canonical cytokine signature to promote glioblastoma progression and chemoresistance.

INTRODUCTION

Temozolomide (TMZ) resistance in glioblastoma (GBM) involves dynamic crosstalk of cancer cells with tumor-associated microglia, but the role of exosomal long non-coding RNAs (lncRNAs) remains poorly defined.

MATERIAL AND

METHODS

We isolated exosomes from TMZ-sensitive (U251) and TMZ-resistant (U251TR) GBM cells. Lnc-DLK1-35 expression was modulated by overexpression/knockdown and validated by RT-qPCR. Exosome internalization by microglia (HMC3 cells) was tracked via PKH67 labeling. Microglial polarization was assessed by studying morphology, marker expression (CD16/CD32/iNOS/Arg-1/CD206/CD163), and cytokine secretion (ELISA: IL-6, TNF-α, TGF-β, IL-10, CXCL13). Functional impact on GBM cells by indirect co-culture with IL4-activated HMC3 cells was examined using CCK-8 and Transwell assays.

RESULTS

Lnc-DLK1-35 was enriched in U251TR cells and their exosomes. GBM exosomes delivered Lnc-DLK1-35 to microglia, inducing a unique GBM-educated phenotype: amoeboid morphology, elevated type 1 macrophage (M1) markers (CD16, iNOS) but suppressed immunoregulatory factors (IL-10, CXCL13). This reprogramming required exosomal transfer. In addition, indirect co-culture with IL4-activated HMC3 cells enhanced GBM malignancy, reduced TMZ sensitivity and promoted migration and invasion.

CONCLUSIONS

Exosomal Lnc-DLK1-35 reprograms cultured microglia cells into a pro-tumorigenic state via a non-canonical cytokine signature, driving TMZ resistance and invasion. Targeting this axis disrupts microglia-GBM communication, revealing a novel therapeutic strategy.