Oligonucleotide G3T19 downregulates CD44 succinylation and inhibits astrocyte-induced glioma immune escape

BACKGROUND: Astrocytes (ACs) play a crucial role within the immune microenvironment of glioma, facilitating its progression. Protein succinylation, a post-translational modification, may serve as a significant regulatory mechanism. SsDNA (single-chain oligonucleotide) drugs with specific sequences for the treatment of tumors have entered clinical trials with remarkable effects. METHODS: G3T19 was evaluated by peroxidase-like activity assay and circular dichroism experiments. The effects of G3T19 on glioma were evaluated by flow cytometry, CCK-8, transwell migration assay, immunohistochemistry, small animal imaging, HPLC, orthotopic xenograft glioma model and human glioma organoid model. The binding of G3T19 and CD44 was examined by immunoprecipitation assay, ELONA assay, immunofluorescence, and docking conformation visualization. The effect of G3T19 on CD44 succinylation was evaluated by mass spectrometry analysis, immunoprecipitation assay, and flow cytometry. RESULTS: G3T19 with G-quadruplex parallel structure binds to CD44 and inhibits AC-enhanced glioma immune escape. CD44 succinylation in ACs adjacent to gliomas is enhanced at lysine 40; however, G3T19 reduces CD44 succinylation to inhibit AC-enhanced glioma immune escape. G3T19-dependent targeting of CD44 reduces NF-κB signaling, PD-L1 expression, and AC-induced glioma immune escape. CONCLUSION: These results confirm that G3T19 binds CD44 and downregulates CD44 succinylation, inhibits NF-κB pathway and the expression of PD-L1, inhibits AC-induced glioma immune escape. This study identifies a new anti-tumor mechanism based on the advanced structure of a functional nucleic acid that may be useful in the development of drugs for glioma immunotherapy.