Abstract 345: Somatic induction of bioluminescent lung tumors in mice.
Authors: Rodriguez Esther , Mannion Liz , D'Santos Paula , Brindle Kevin M. , Lyons Scott K. 
Published: August 2014

Genetically engineered (GEM) mouse models of cancer currently comprise the most accurate phenocopies of the human disease available to researchers. It is therefore highly desirable that these models be used beyond tumor etiology studies and to evaluate the efficacy of novel therapeutic treatment strategies. Complicating the application of these models for such purposes, however, is that tumor onset and progression are stochastic and cannot be visualized directly when developing within internal organs. Therefore it is often challenging to know when to start treatment or how to assess tumor response to treatment.

Bioluminescence imaging is a highly sensitive and relatively high-throughput preclinical imaging modality well suited to overcoming the inherent difficulties of applied research with GEM's. We describe here a series of new lentiviral vectors that can be used to infect somatic cells in the mouse and to induce bioluminescent tumors, without the need to develop additional transgenic reporter strains of mice or extensive breeding.

The basic vector contains a tamoxifen-inducible and self-inactivating Cre recombinase, as well as conditional firefly luciferase and mStrawberry transgenes. As proof of concept, we administered our vector (1x106 lentiviral particles) to the lungs of mice possessing conditional KrasG12D and homozygously floxed p53 alleles via intranasal instillation in an attempt to induce bioluminescent non-small cell lung adenocarcinoma (NSCLC). This approach gave rise to between two and five bioluminescent lung lesions per mouse, some of which showed evidence of progressing from low to high-grade adenocarcinoma at 7 months post-vector administration and induction. Further, we could accelerate the development of tumors from KrasG12D only mice with a variant lentiviral construct that additionally expressed a shRNA against mouse p53. Light originating from infected and recombined cells increased over the course of the experiment in all mice, indicative of an expansion in the number of luciferase labeled cells and tumor development. Our imaging sensitivity was also very high and light could be detected and monitored at all stages post-Cre induction.

A significant advantage of our approach to modelling tumorigenesis in this manner is its versatility. Spontaneous tumors can be induced and rendered imageable without the development or breeding of new transgenic reporter mouse strains. Further, the expression of additional tumor-related genes may be introduced (subject to virus packaging limits) or knocked-down in somatic cells of the base model, again without necessitating the development or breeding of additional transgenic mice. These vectors should also be useful for inducing imageable tumors in organs other than the lung provided that the tumor genetics are highly penetrant and that the cells are permissible to infection with a VSV-G pseudotyped lentiviral particle.

Citation Format: Esther Rodriguez, Liz Mannion, Paula D'Santos, Kevin M. Brindle, Scott K. Lyons. Somatic induction of bioluminescent lung tumors in mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 345. doi:10.1158/1538-7445.AM2013-345