Use of Reporter Genes for Optical Measurements of Neoplastic Disease In Vivo

Abstract

Revealing the cellular and molecular changes associated with cancer, as they occur in intact living animal models of human neoplastic disease, holds tremendous potential for understanding disease mechanisms and elucidating effective therapies. Since light is transmitted through mammalian tissues, at a low level, optical signatures conferred on tumor cells by expression of reporter genes encoding bioluminescent and fluorescent proteins can be detected externally using sensitive photon detection systems. Expression of reporter genes, such as the bioluminescent enzyme firefly luciferase (Luc) or variants of green fluorescent protein (GFP) in transformed cells, can effectively be used to reveal molecular and cellular features of neoplasia in vivo. Tumor cell growth and regression in response to various therapies have been evaluated non-invasively in living experimental animals using these reporter genes. Detection of Luc-labeled cells in vivo was extremely sensitive with signals over background from as few as 1000 human tumor cells distributed throughout the peritoneal cavity of a mouse with linear relationships between cell number and signal intensity over five logs. GFP offers the strength of high-resolution ex vivo analyses following in vivo localization of the tumor. The dynamic range of Luc detection allows the full disease course to be monitored since disease progression from small numbers of cells to extensive disease can be assessed. As such, therapies that target minimal disease as well as those designed for late stage disease can be readily evaluated in animal models. Real time spatiotemporal analyses of tumor cell growth can reveal the dynamics of neoplastic disease, and facilitate rapid optimization of effective treatment regimens. Thus, these methods improve the predictability of animal models of human disease as study groups can be followed over time, and can accelerate the development of therapeutic strategies.

Non-invasive gamma camera imaging of gene transfer using an adenoviral vector encoding an epitope-tagged receptor as a reporter

“…[2][3][4][5][6][7] These techniques offer high spatial resolution, but may be difficult to quantitate and detect depending upon the depth issue in animal models. The transferrin receptor and b-galactosidase have been used as reporter genes for magnetic resonance imaging with iron oxide nanoparticles and a gadolinium chelate, respectively.…”

Stem Cell Monitoring with a Direct or Indirect Labeling Method

“…(Fig. 4) [19,[51][52][53][54][55][56][57][58][59]. Reporter genes consist of gene regulatory elements, such as promoters and enhancers, which drive the reporter gene DNA sequence and poly A sequence providing stabilization on the final product.…”

Molecular imaging of gene therapy for cancer

“…Sensitive imaging systems have been built to detect and quantitate small numbers of cells or organisms expressing luciferase as a transgene. [73][74][75] BLI has been used to monitor tumor cell growth and regression, 76,77 to visualize the kinetics of tumor cell clearance by chemotherapeutics 78 and to track gene expression. 36 Luciferase imaging has recently revealed gene transfer to tumors followed by a decrease in transgene expression with tumor cell death over time.…”