Relationship between glucose transporter, hexokinase and FDG-PET in esophageal cancer

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has been established as a powerful diagnosing modality in clinical oncology. FDG accumulation has been demonstrated to correlate with hexokinase activity. However, recent reports suggest that glucose transporters participate in FDG accumulation. The aim of this study is to evaluate glucose transporter and hexokinase expression and clarify the relationship between them and FDG accumulation.

FDG-PET was performed in 72 preoperative patients with esophageal cancer. The ratios of tumor radioactivity to plasma radioactivity (Ci/Cp values) were obtained 60 minutes after administration. We studied the expressions of glucose transporter 1 (Glut1) and type-II hexokinase (HK-II) by immunohistochemical analysis of the resected specimen. The percentages of cells expressing Glut1 and HK-II were scored on a 5-point scale (1=0-20%, 2=20-40%, 3=40-60%, 4=60-80%, 5=80-100%). Then the 3 scores obtained from 3 counting trials were averaged to give the Glut-index and HK-index.

All esophageal cancers showed marked FDG accumulation. All 72 cancers expressed Glut1 and 71 of 72 cancers expressed HK-II. The Glut-index had a weak correlation with the Ci/Cp value (not significant). The HK-index had a close positive correlation with the Ci/Cp value (p<0.005).

FDG accumulation correlates more with type-II hexokinase expression than with glucose transporter 1 expression.