Overexpression of dimethylarginine dimethylaminohydrolase enhances tumor hypoxia: an insight into the relationship of hypoxia and angiogenesis in vivo.
The oxygenation status of tumors derived from wild-type C6 glioma cells and clone D27 cells overexpressing dimethylarginine dimethylaminohydrolase (DDAH) was assessed in vivo using a variety of direct and indirect assays of hypoxia. Clone D27 tumors exhibit a more aggressive and better-vascularized phenotype compared to wild-type C6 gliomas. Immunohistochemical analyses using the 2-nitroimidazole hypoxia marker pimonidazole, fiber optic OxyLite measurements of tumor pO2, and localized 31P magnetic resonance spectroscopy measurements of tumor bioenergetic status and pH clearly demonstrated that the D27 tumors were more hypoxic compared to C6 wild type. In the tumor extracts, only glucose concentrations were significantly lower in the D27 tumors. Elevated Glut-1 expression, a reliable functional marker for hypoxia-inducible factor-1-mediated metabolic adaptation, was observed in the D27 tumors. Together, the data show that overexpression of DDAH results in C6 gliomas that are more hypoxic compared to wild-type tumors, and point strongly to an inverse relationship of tumor oxygenation and angiogenesis in vivo--a concept now being supported by the enhanced understanding of oxygen sensing at the molecular level.
Kostourou
Vassiliki
V
Department of Basic Medical Sciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
Troy
Helen
H
Murray
Joanne F
JF
Cullis
Elizabeth R
ER
Whitley
Guy St J
GS
Griffiths
John R
JR
Robinson
Simon P
SP
D000581:Amidohydrolases / Q000235:genetics*; D000818:Animals; D001932:Brain Neoplasms; D015687:Cell Hypoxia / Q000235:genetics*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D005910:Glioma; D051272:Glucose Transporter Type 1; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000235:genetics*; D009593:Nitroimidazoles / Q000032:analysis*; D011838:Radiation-Sensitizing Agents; D051381:Rats; D014162:Transfection; D014183:Transplantation, Heterologous
D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins; D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C495677:SLC2A1 protein, human; C495678:Slc2a1 protein, mouse; C495679:Slc2a1 protein, rat; C033815:pimonidazole; D000581:Amidohydrolases; C059999:dimethylargininase