Effect of low glutamine/glucose on hypoxia-induced elevation of hypoxia-inducible factor-1alpha in human pancreatic cancer MiaPaCa-2 and human prostatic cancer DU-145 cells.
OBJECTIVE
Tumor microenvironment is characterized by regions of fluctuating and chronic hypoxia, low extracellular pH, and nutrient depletion. Although it is well known that hypoxia stimulates the accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha), the role of low extracellular pH and nutrient depletion on hypoxia up-regulation of HIF-1alpha is not well known. In this study, human pancreatic cancer MiaPaCa-2 and human prostatic cancer DU-145 cells were exposed to hypoxia in the presence or absence of glucose, glutamine, and/or pyruvate.


RESULTS
We observed that low glucose and low glutamine, but not low pyruvate, effectively suppressed the elevation of HIF-1alpha level during hypoxia (0.1-1% oxygen). Deprivation of glutamine or glucose inhibited the accumulation of HIF-1alpha in the presence of MG-132, a protease inhibitor, regardless of oxygen tensions. Data from reverse transcription-PCR analysis revealed that the levels of HIF-1alpha mRNA were not significantly changed at different concentrations of glutamine or glucose under hypoxia. The amount of HIF-1alpha suppression was proportional to protein synthesis inhibition.


CONCLUSIONS
Our data suggest that glutamine or glucose deprivation inhibits the accumulation of HIF-1alpha under hypoxic conditions by disrupting translational processes rather than transcriptional or proteasomal degradation processes.
Department of Surgery and Pharmacology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
Seok Joon
SJ
Kwon
Yong J
YJ
Lee
D015153:Blotting, Western; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D005973:Glutamine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D005973:Glutamine; D046988:Proteasome Endopeptidase Complex; D005947:Glucose