Quantitative gene expression underlying 18f-fluorodeoxyglucose uptake in colon cancer.

Abstract

653 Background: Positron emission tomography (PET) with the glucose analogue 18F-fluorodeoxyglucose (FDG) is widely used in oncologic imaging. This study examines the molecular mechanism underlying the detection of colon cancer (CC) by FDG-PET. Methods: Pre-operative PET/CT scans and tissue samples from primary CC and surrounding normal mucosa were obtained from 42 patients. FDG uptake was quantified using maximal standardized uptake value (SUVmax). The expression of ki67, glucose transporter 1 (GLUT-1), hexokinase 1 (HK1), hexokinase 2 (HK2), vascular endothelial growth factor (VEGF), hypoxia-inducible factor 1α (HIF1α) and carbonic anhydrase IX (CaIX) mRNA was examined by quantitative real time reverse transcriptase-polymerase chain reaction. Results: All primary tumours showed increased uptake of FDG. The mean SUVmax was 15.0 (range 5.3 – 37.8). No correlation was found between tumour size and SUVmax. Mean gene expression levels of GLUT1, HK2, ki67, HIF1α, VEGF and CaIX, but not HK1, were significantly higher in primary tumours than in surrounding normal colonic mucosa. Linear regressions pairing tumour SUVmax with gene expression levels showed significant correlations between SUVmax and HK2, ki67 and CaIX, respectively. Conclusions: These results confirm FDG PET/CT as a functional imaging method in CC, and that FDG accumulation reflects molecular events related to glycolysis, cell proliferation, hypoxia, but not angiogenesis.