Hyperbaric Oxygen Reverses High-Glucose–Induced Stemness and Radioresistance in Non-Small Cell Lung Cancer Cells

Jui-Ying Lee,1,2,* Chia-Li Chung,3,4,* Tzu-Ting Tseng,5 Shih-Hsun Kuo,6 Yu-Peng Liu,1,7 Ming-Tsang Wu,8,9 Hung-Pei Tsai,4,5,10 Aij-Lie Kwan1,5,11,12 1Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan; 2Division of Thoracic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung City, Taiwan; 3Division of Neurosurgery, Department of Surgery, Kaohsiung Municipal Siaogang Hospital, Kaohsiung City, Taiwan; 4Department of Surgery, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan; 5Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung City, Taiwan; 6Department of Radiation Oncology, Kaohsiung Medical University Hospital Kaohsiung Medical University, Kaohsiung City, Taiwan; 7Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan; 8PhD Program in Environmental and Occupational Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan; 9Department of Family Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung City, Taiwan; 10Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung City, Taiwan; 11Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung City, Taiwan; 12Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan*These authors contributed equally to this workCorrespondence: Hung-Pei Tsai, Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, No. 100, Shiquan 1st Road, Sanmin Dist, Kaohsiung City, 807378, Taiwan, Tel +886 7 3121101, Email [email protected] Aij-Lie Kwan, Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, No. 100, Shiquan 1st Road, Sanmin Dist, Kaohsiung City, 807378, Taiwan, Tel +886 7 3121101, Email [email protected]: Hyperglycemia may promote aggressive phenotypes and treatment resistance in non-small cell lung cancer (NSCLC). We investigated whether chronic high glucose (HG) exposure induces stem cell-like properties and radioresistance and whether hyperbaric oxygen (HBO) reverses these effects.Methods: H1299 and A549 cells were maintained under normal glucose (NG; 5.5 mM D-glucose) or high glucose (HG; 25 mM D-glucose) conditions. Acute effects were evaluated by switching NG-grown cells to NG or HG and performing MTT assays. For all other experiments, cells were conditioned in HG for 3 months. Protein expression of glucose transporter-1 (Glut1), hypoxia-inducible factor-1α (HIF-1α), CD133, SOX2, and OCT4 was assessed by immunoblotting. Stem-like behavior and radiosensitivity were evaluated by tumorsphere formation and clonogenic survival assays following irradiation. HBO (100% O2, 1.5 ATA, 90 min/session, once daily) was applied as indicated.Results: Acute HG increased cell viability, whereas long-term HG conditioning did not significantly alter short-term viability but increased tumorsphere formation and clonogenic survival after irradiation. HG upregulated Glut1 and HIF-1α and increased SOX2 and OCT4 expression. Additional analyses showed that 4 weeks, but not 1 week, of continuous HBO exposure reduced HIF-1α, SOX2, and OCT4 expression under HG conditions, whereas Glut1 expression was not markedly altered. HBO suppressed HG-enhanced tumorsphere formation and reversed HG-associated radioresistance.Conclusion: Chronic HG promoted stem-like and radioresistant phenotypes in NSCLC cells. Prolonged HBO exposure for 4 weeks attenuated these effects and was associated with reduced HIF-1α, SOX2, and OCT4 expression, supporting HBO as a potential preclinical adjunct strategy for mitigating HG-associated therapeutic resistance.Keywords: non-small cell lung cancer, hyperglycemia, high glucose, hyperbaric oxygen, radioresistance, cancer stem-like cells