Regulation of temozolomide resistance in glioma cells via the RIP2/NF-κB/MGMT pathway

Background: Temozolomide (TMZ) is a first-line chemotherapy drug for the treatment of malignant glioma and resistance to it poses a major challenge. Receptor-interacting protein 2 (RIP2) is associated with the malignant character of cancer cells. However, it remains unclear whether RIP2 is involved in TMZ resistance in glioma. Methods: RIP2 expression was inhibited in TMZ-resistant glioma cells and normal glioma cells by using small interfering RNA (siRNA) against RIP2. Plasmid transfection method was used to overexpress RIP2. Cell counting kit-8 assays were performed to evaluate cell viability. Western blotting or immunofluorescence was performed to determine RIP2, NF-kappa B, and MGMT expression in cells. Flow cytometry was used to investigate cell apoptosis. TMZ-resistant glioma xenograft models were established to evaluate the role of the RIP2/NF-kappa B/MGMT signaling pathway in drug resistance. Results: We observed that RIP2 expression was upregulated in TMZ-resistant glioma cells, whereas silencing of RIP2 expression enhanced cellular sensitivity to TMZ. Similarly, upon the induction of RIP2 overexpression, glioma cells developed resistance to TMZ. The molecular mechanism underlying the process indicated that RIP2 can activate the NF-kappa B signaling pathway and upregulate the expression of O6-methylguanine-DNA methyltransferase (MGMT), following which the glioma cells develop drug resistance. In the TMZ-resistant glioma xenograft model, treatment with JSH-23 (an NF-kappa B inhibitor) and lomeguatrib (an MGMT inhibitor) could enhance the sensitivity of the transplanted tumor to TMZ. Conclusion: We report that the RIP2/NF-kappa B/MGMT signaling pathway is involved in the regulation of TMZ resistance. Interference with NF-kappa B or MGMT activity could constitute a novel strategy for the treatment of RIP2-positive TMZ-resistant glioma.