Abstract
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Objectives FDG is the most widely used PET tracer. Previous observations obtained by us and others report variable and sometimes poor spatial and quantitative correlation between FDG and the major glucose transporter GLUT1. To address this puzzling phenomenon we analyzed the distribution of GLUT 1, GLUT 3 and the glucose phosphorylation enzyme Hexokinase II in viable, necrotic and inflammatory regions of rat mammary tumors.
Methods Rat mammary tumor (RMT) cells were inoculated in the interscapular region of Lewis rats. Tumors were removed and fixed with 3.7% formaldehyde. The tumors were embedded with paraffin and 4μm thick sections were made. Immunostaining of GLUT-1, GLUT-3, hexokinase II and anti-macrophage (human CD68) antibodies were carried out in successive tumor sections.
Results Expression of GLUT-1 was focal and found near necrotic areas. GLUT-3 expression was dispersed and found only in necrotic and inflammatory areas. Expression of hexokinase II distributed uniformly throughout almost the entire tumor section. The distribution of GLUT-3 expression was similar to that of cells stained with anti-macrophage (human CD68) antibody.
Conclusions This study revealed poor quantitative and spatial correlation between the expression of hexokinase II and GLUT 1. This mismatch may underlie the limited association of FDG and GLUT 1, observed in mammary and other types of tumors. The dispersed expression of GLUT 3 and its confinement to inflammatory and necrotic areas suggest its limited role in the assessment of FDG distribution in mammary tumor