Author: Scott James Bright, Hadil Elldakli, Mojtaba Hoseini-Ghahfarokhi, Rishab Kolachina, Poliana Marinello, Yogesh Rai, Marco Freitas Reis, Gabriel O. Sawakuchi, Walison Augusto Silva Brito, Mark Wasley ๐จโ๐ฌ
Affiliation: MD Anderson Cancer Center, MD Anderson, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, MD Anderson Cancer Center, Medical College of Georgia ๐
Purpose:
Glutaminase 1 (GLS1) is an intracellular enzyme crucial for generating antioxidants such as glutathione (GSH). GSH neutralizes reactive oxygen species (ROS) induced by radiotherapy. About 15% of lung cancers have mutations in KEAP1, which increase their ability to produce GSH to neutralize ROS, making KEAP1 mutant lung cancer cells radioresistant. Our hypothesis is that inhibiting GLS1 with the small molecule inhibitor called IACS-6274 overcomes radioresistance in KEAP1 mutated lung cancer by impeding oxidative stress defense, leading to cell death.
Methods:
We used NCI-H460 lung cancer cells, which is KEAP1 mutated. Cells were exposed to 6 MV x-rays or 3.85 keV/ฮผm dose weighted LET protons and cell survival was measured using the clonogenic survival assay. We also measured the ratio of reduced to oxidized GSH using the GSH/GSSG-Glo Assay (Promega) to indicate the cellsโ ability to respond to oxidative stress. We measured various oxidative stress markers including total levels of reactive oxygen species, mitochondrial superoxide and lipid peroxidation.
Results:
Cells were radiosensitized with IACS-6274 with a significant reduction in the dose to reduce survival to 10% (D10%) for both photons and protons. The ratio of reduced to oxidized GSH was lower in cells treated with IACS-6274. All oxidative stress markers were increased with radiation and radiation combined with IACS-6274. This was particularly evident for mitochondrial superoxide levels.
Conclusion:
Our results indicate that disrupting metabolism in KEAP1 mutant lung cancer cells affects their ability to cope with radiation-induced ROS, subsequently leading to radiosensitization. Our data supports a role for inhibition of metabolism as a mechanism to combat radioresistance of KEPA1 mutation lung cancer.