Non-Invasive In Vivo Imaging and Quantification of Tumor Growth and Metastasis in Rats Using Cells Expressing Far-Red Fluorescence Protein.

Jon Christensen,Daniel Vonwil,V. Prasad Shastri,Juri G. Gelovani

doi:10.1371/journal.pone.0132725

Abstract

Non-invasive in vivo imaging is emerging as an important tool for basic and preclinical research. Near-infrared (NIR) fluorescence dyes and probes have been used for non-invasive optical imaging since in the NIR region absorption and auto fluorescence by body tissue is low, thus permitting for greater penetration depths and high signal to noise ratio. Currently, cell tracking systems rely on labeling cells prior to injection or administering probes targeting the cell population of choice right before imaging. These approaches do not enable imaging of tumor growth, as the cell label is diluted during cell division. In this study we have developed cell lines stably expressing the far-red fluorescence protein E2-Crimson, thus enabling continuous detection and quantification of tumor growth. In a xenograft rat model, we show that E2-Crimson expressing cells can be detected over a 5 week period using optical imaging. Fluorescence intensities correlated with tumor volume and weight and allowed for a reliable and robust quantification of the entire tumor compartment. Using a novel injection regime, the seeding of MDA-MB-231 breast cancer cells in the lungs in a rat model was established and verified.

Highlights

Tumor growth and dissemination are complex processes that are not readily recapitulated in vitro
Using MDA-MB-231 stably expressing the far-red fluorescence protein E2-Crimson, the growth of tumors in rats and its associated cellularity was followed over time using Fluorescence tomography (FT) and ability to visualize tumor cell seeding to the lungs was demonstrated
FT derived tumor volumes were correlated to tumor volumes determined using traditional techniques

Summary

Introduction

Tumor growth and dissemination are complex processes that are not readily recapitulated in vitro. The tumor environment is highly complex and it presents a heterogeneous cellular composition that undergoes spatiotemporal changes, which concurrently alters the tumor microenvironment in the cellular composition. This poses many challenges with regards to tumor targeting and therapy. During the progression of a tumor, the increase in tumor volume is a combined manifestation of proliferation of tumor cells, influx of stromal cells such as mesenchymal cells, endothelial cells, tumor-associated macrophages as well as immune cells, and production of extra-cellular-matrix (ECM) [1,2,3,4,5,6]. Understanding the temporal changes to the various components within a tumor can aid in the development of improved and customized.

Objectives

Methods

Results

Conclusion