High-dose radiation-resistant lung cancer cells stored many functional lipid drops through JAK2/p-STAT3/FASN pathway.

backgroundThe understanding of radiation resistance is still unclear. This study aims to explore the new mechanism of radiation resistance in lung cancer from the perspective of lipid metabolism.

methodsOil red O was used to detect the amount of lipid droplets in high-dose radiation-resistant lung cancer cells (HDRR-LCCs) and the primary lung cancer cells. Western blot analysis was used to determine the protein expression levels of key molecules related to de novo fatty acid synthesis and fatty acid transport. Orlistat was used to inhibit the de novo fatty acid synthesis. The prediction of the transcriptional regulators of fatty acid synthetase (FASN) was analyzed by bioinformatics. AZD-1480 was used to inhibit the JAK2/STAT3 pathway to observe its effects on FASN and intracellular lipid droplets. The regulation of the transcription factor p-STAT3 on the FASN gene was verified by Chip-qPCR. Finally, we used the public data of lung cancer patients to analyze the correlation between FASN and LPL gene expression with the prognosis.

resultsThere were more lipid drops in the HDRR-LCCs than in the primary lung cancer cells. HDRR-LCCs preferred de novo synthesis of fatty acids, and high expression of LPL homodimers indicated a high intake of extracellular fatty acids. The expression of FASN was increased in HDRR-LCCs compared with the primary lung cancer cells in a radiation-dose-dependent way, while LPL homodimers did not show such a trend. The lipid droplets, cell proliferation, and radiation resistance were decreased in HDRR-LCCs after orlistat treatment. Lipid droplets were significantly reduced, and the protein expression of FASN also decreased when using AZD-1480 to inhibit the JAK2/STAT3 pathway. The Chip-qPCR showed that p-STAT3 was the upstream regulator which binds to the promoter region of FASN. Survival analysis showed that high expression of the FASN gene was associated with a poor prognosis in lung cancer patients who received radiotherapy.

conclusionOur studies discovered that lipids deposited in HDRR-LCCs were due to endogenous de novo fatty acids synthesis and exogenous lipids uptake. JAK2/p-TAT3/FASN could be used as promising targets for radiotherapy sensitization. Our study provided a new theoretical basis for studying the mechanism of radiation resistance in lung cancer.