Non-invasive PET Imaging of Human Breast Xenografts: Influence of Tumor Hypoxia

摘要

The first year research has focussed on two studies. One is to develop a method that can non-invasively detect the hypoxic cell foci in malignant tumors. The iodo-azomycin galactoside (IAZG) was labeled with long- lived positron emitter, 1251, as a PET radiotracer. In vitro experiments showed that the cellular uptake of IAZG was inversely related to the intracellular oxygen concentration. The pO2-dependent IAZG uptake was investigated for 8 human cell lines including two breast cancer lines. This showed the highest uptake in two breast cancer cell lines. We are now evaluating the use of this agent in vivo together with regional blood flow in the tumor. Another study is to investigate the hypoxic cell fraction (HCF) as a function of tumor size. The well developed paired survival assay and the tissue pO2 measurements (using an OxyLite system) were compared. The HCF was 10% in small tumors (<200 mm3), but increased to 35-50% in a tumor of 200 mm3. Above this tumor size, the HOF was consistent. As compared to paired survival assay, the direct pO2 measurements tend to show the larger HCF, specifically in large tumors.