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


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.


CONCLUSIONS
The radiation sensitivity of the human melanoma cell lines was changed only to a minor extent by transient exposure to hypoxia.
Danielsen
T
T
Department of Biophysics, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, Oslo.
Skøyum
R
R
Rofstad
E K
EK
D002352:Carrier Proteins / Q000096:biosynthesis; D002453:Cell Cycle; D015687:Cell Hypoxia; D000091342:Endoplasmic Reticulum Chaperone BiP; D004734:Energy Metabolism; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis; D006360:Heat-Shock Proteins; D006801:Humans; D008545:Melanoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008565:Membrane Proteins / Q000096:biosynthesis; D018832:Molecular Chaperones / Q000096:biosynthesis; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; C018551:glucose-regulated proteins