Abstract
HIF-1 protein over-expressed by malignant tumors is frequently associated with a higher mortality rate and a poor recovery. If a non-invasive system can be developed to detect the expression of HIF-1 at its early stage or during tumor progression or treatment, this may serve as a good reference for medical examination and diagnosis and to help practitioners modify their treatment procedures if necessary. The aim of this research was to contruct a hypoxia response element (HRE; 5'-RCGTG-3') driving vectors simultaneously expressing two reporter proteins, enhanced green fluorescent protein (EGFP) and Renilla luciferase. These reporter vectors were then transfered into a murine prostate cancer cell line, TRAMP-C1. The expression of these reporters were examined in vitro using either hypoxia mimic reagent, deferoxamine (DFX), or hypoxic chamber (1% O2, 5% CO2, 94% N2). After 24 hours of incubation in either condition, we found that both the fluorescence and bioluminescence signals could be dectected in TRAMP-EGFP-HRE-Rluc cells by fluorescent microscopy and bioluminescent assay, respectively. The expression of these vectors in growing tumors was measured by IVIS imaging system. Results showed that tumors growing in pre-irradiated tumor bed has stronger bioluminescence and bioluminescence resonance energy transfer (BRET) than those growing in control tumor bed. The in vivo imagings were verified by ex vivo assay using bioluminescent imaging, BRET imaging, fluorescence analysis by flowcytometer and luminescence analysis. In summary, we have successfully established a non-invasive HIF-1 detection system to monitor the hypoxia development during tumor progression.