Imaging of luciferase and GFP‐transfected human tumours in nude mice

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Abstract
Studies were performed to compare green fluorescent protein (GFP)‐transfected and firefly luciferase (Luc)‐transfected MCF‐7 human breast tumour cells both in vitro and in vivo. For in vitro studies, cells were serially diluted in 96‐well microplates and analysed using a NightOwl LB 981 Molecular Light Imager and a Victor multilabel reader. For in vivo studies, nude mice were injected either intraperitoneally, intravenously or subcutaneously with transfected cells and then imaged using the NightOwl Imager after intraperitoneal injection of d‐luciferin for Luc tumours, or excitation at 470 nm for GFP tumours. In vitro imaging studies revealed that both GFP and Luc transfectants were quantifiable. However, the Luc‐transfected cells were detectable at a significantly lower concentration compared to GFP transfectants. In vivo studies demonstrated that GFP‐transfected tumours were detectable as subcutaneous and intraperitoneal tumours but not as deep tissue lesions, whereas Luc‐transfected tumours were detectable as subcutaneous and intraperitoneal tumours and as deep tissue lesions resulting from intraperitoneal or intravenous inoculation. These findings demonstrate that GFP‐transfected cells may be useful for imaging studies of superficial tumours where both excitation and emission wavelengths are able to penetrate tissues, whereas luciferase‐transfected cells appear superior for imaging studies of primary and metastatic tumours in distant sites and deep tissues. Copyright © 2003 John Wiley & Sons, Ltd.