Hypoxia-induced changes in radiation sensitivity in human melanoma cells: importance of oxygen-regulated proteins, adenylate energy charge and cell cycle distribution

• Published in: Radiotherapy and oncology Vol. 44; no. 2; pp. 177 - 182
• Main Authors: Danielsen, Turi, Skøyum, Rubi, Rofstad, Einar K.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01-08-1997
• Subjects: Adenylate energy charge; Carrier Proteins - biosynthesis; Cell Cycle; Cell cycle distribution; Cell Hypoxia; Energy Metabolism; Heat-Shock Proteins; HSP70 Heat-Shock Proteins - biosynthesis; Humans; Hypoxia; Melanoma - metabolism; Melanoma - pathology; Melanoma - radiotherapy; Membrane Proteins - biosynthesis; Molecular Chaperones - biosynthesis; Oxygen-regulated proteins; Radiation sensitivity; Radiation Tolerance; Tumor Cells, Cultured; Adenylate energy charge; Hypoxia; Radiation sensitivity; Cell cycle distribution; Oxygen-regulated proteins
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/S0167-8140(97)01929-4

Background and purpose: The effects of transient hypoxia on the radiation sensitivity of human tumour cells have so far been investigated only to a limited extent, and only up to 12 h after reoxygenation. We irradiated cells shortly after reoxygenation (<1 h) or at prolonged times after reoxygenation (24 h and 48 h) in order to examine possible relationships between changes in radiation sensitivity on the one hand and changes in rates of synthesis of oxygen-regulated proteins, changes in energy metabolism and changes in cell cycle distribution on the other.
Materials and methods: Four human melanoma cell lines (A-07, D-12, R-18 and U-25) were included in the study. After hypoxia treatment (4 h or 16 h) and reoxygenation, cells were either irradiated as monolayers at a dose rate of 2.0 cGy/min or prepared for protein analysis, energy charge measurements or flow cytometric measurements of DNA.
Results: U-25 was the only line that showed increased radiation sensitivity shortly after reoxygenation, possibly because of extensive energy depletion. A-07 was the only line that showed increased radiation sensitivity at prolonged times after reoxygenation, possibly because of hypoxia-induced changes in the cell cycle distribution. The rates of synthesis of oxygen-regulated proteins (GRP78, GRP94, HSP70 and HSP90) were transiently perturbed to a similar extent in all lines after hypoxia treatment.
Conclusion: The radiation sensitivity of the human melanoma cell lines was changed only to a minor extent by transient exposure to hypoxia.