RIP2/NF-κB/PD-L1 signaling pathway is involved in temozolomide resistance by inducing autophagy in glioblastoma cells.

Autophagy is an important factor in temozolomide (TMZ) resistance in glioblastoma (GBM). Receptor-interacting protein 2 (RIP2) is associated with autophagy, but its role and mechanism in regulating autophagy in GBM cells remain unclear. To analyze RIP2 expression in GBM in The Cancer Genome Atlas (TCGA) dataset. GBM cells were stimulated using recombinant human RIP2 protein (rRIP2) or RIP2 plasmid. Cell proliferation and apoptosis were assessed using CCK-8 assay and flow cytometry. Western blotting and immunofluorescence (IF) assays were performed to detect protein expression in cells and tumor tissues. Moreover, the relationship between RIP2-induced autophagy and TMZ resistance was verified in a GBM xenograft model. We determined that RIP2 expression was upregulated in GBM. rRIP2 and RIP2 overexpression induced TMZ resistance in the GBM cell lines. RIP2 overexpressing xenograft tumors have reduced sensitivity to TMZ. In addition, we showed that PD-L1 protein expression was upregulated in GBM tissues with RIP2 overexpression. rRIP2 and RIP2 overexpression induced autophagy in GBM cells through AMPK. Notably, RIP2 upregulated PD-L1 expression through the NF-κB signaling pathway, which induced autophagy and TMZ resistance in GBM cells. Moreover, NF-κB or autophagy inhibition reversed TMZ resistance in RIP2 overexpressing GBM cells in a xenograft model. In conclusion, RIP2 induces TMZ resistance in GBM cells by promoting autophagy through the NF-κB/PD-L1 signaling pathway, indicating that the RIP2/NF-κB/PD-L1 pathway may be therapeutic target for TMZ resistance.