Investigation of The Effects of cGAS/STING Pathway and PTEN Mutations on Temozolomide Response in Glioblastoma Cells
Project no. 21423 · Status: Kapanmış · 2020
Summary
Glioblastoma (GBM) is a primary brain tumour with high mortality rate, and it is characterized by treatment resistance and recurrence. Currently following the surgery, adjuvant radiotherapy and temozolomide (TMZ) are commonly used in the treatment of GBM. There is no alternative therapy option in the recurrent cases resistant to TMZ and radiotherapy. Therefore, new therapies are urgently needed to target various mechanisms over different molecules that have function in the progression and treatment resistance of GBM. It has been shown that PTEN, one of the tumour suppressor genes, is frequently mutated in GBM cases and these mutations are associated with poor prognosis. The cGAS/STING is a cytosolic DNA-sensing pathway that senses to the cytoplasmic DNA and activates type-I interferons (IFNs) and other cytokines and triggers innate immunity. In this study we aimed to determine the cGAS/STING activation in the PTEN-harbouring T98G and PTEN-deficient U118MG cell lines in the TMZ response and investigate the usability of STING agonists (S.A) to enhance the effects of TMZ. For this purpose, we performed proliferation, cytotoxicity, qRT-PCR, Western Blot and Elisa analyses. We determined that SA treatment increased the cytotoxic effect of TMZ in the T98G cell line. However, SA exposure did not change the cytotoxic effect of TMZ in the PTEN deficient U118MG cell line. We found that the combined treatment with TMZ and S.A caused a significant increase in IRF3, STING, NF-?B and RELA expressions in the T98G cell line. However, our results showed that expressions of all target proteins were lower in the U118MG cell line and STING protein was not expressed at all. It was noticed that IFN-? and IL-6 levels were up regulated in the T98G cell line compared to the U118MG cell line, but there were no significant differences between the treatment groups. Overall, all these data give evidence that the STING agonist can increase the TMZ response depending on the PTEN activity, our findings need to be supported by further analysis and in vivo studies.