Spying on cancerMolecular imaging in vivo with genetically encoded reporters

Abstract

Genetically encoded imaging reporters introduced into cells and transgenic animals enable noninvasive, longitudinal studies of dynamic biological processes in vivo. The most common reporters include firefly luciferase (bioluminescence imaging), green fluorescence protein (fluorescence imaging), herpes simplex virus-1 thymidine kinase (positron emission tomography), and variants with enhanced spectral and kinetic properties. When cloned into promoter/enhancer sequences or engineered into fusion proteins, imaging reporters allow transcriptional regulation, signal transduction, protein-protein interactions, oncogenic transformation, cell trafficking, and targeted drug action to be spatiotemporally resolved in vivo. Spying on cancer with genetically encoded imaging reporters provides insight into cancer-specific molecular machinery within the context of the whole animal.

Quantifying intra‐osseous growth of osteosarcoma in a murine model with radiographic analysis

“…4 Therefore, analysis of both aspects of osteosarcoma progression necessitates that at least one parameter be monitored in vivo. Current methods for monitoring the longitudinal development of tumor include direct measurement of tumor cells genetically tagged with fluorescent proteins or luciferase 4,11,12 and indirect tumor burden estimation using external calipers to measure soft tissue surrounding the primary tumor. 6 Although useful, these methods have limitations.…”

“…6 Although useful, these methods have limitations. The use of fluorescence or luminescence imaging requires prior genetic manipulation of the tumor cell 11,12 and the ultimate visual signal typically requires injection of a substrate measured with potential subjective statistical error. 16 The alternative method, quantification by calipers has the advantage that it does not require genetic manipulation of the cell; however it does not account for the loss of anatomic landmarks during tumor development.…”

“…Methods for quantifying osteosarcoma longitudinally include direct measurement of tumor cells genetically tagged with fluorescent proteins or luciferase 4,11,12 and indirect tumor burden estimation using external calipers to measure the area or volume from two-dimensional measurements. 6,13 Here, we propose a novel approach to monitor longitudinal growth of intra-osseous tumor by radiographic analysis.…”

Optical imaging for the new grammar of drug discovery

“…Reporter gene technology can be broadly classified into enzymatic reporter systems (b-galactosidase, luciferase and b-lactamase) and fluorescent proteins [24][25][26]. In an enzymatic reporter system, photons are generated through chemical reactions and therefore called bioluminescence, whereas fluorescent proteins emitting light when excited by a photon of particular energy refers to fluorescence.…”

On In Vivo Imaging in Cancer

“…In particular, integration of genetically encoded imaging reporters into live cells and small animal models of cancer has provided powerful tools to monitor cancer-associated molecular, biochemical, and cellular pathways in vivo (Gross and Piwnica-Worms 2005). New animal models combined with imaging techniques (nuclear, fluorescence, and bioluminescence) at both macroscopic and microscopic scales will make it possible to explore the consequences of the interactions between tumor cells and microenvironment during tumor progression and between stromal cells and normal epithelial cells during normal morphogenesis in vivo in real time.…”