Versatile and enhanced tumour modelling in mice via somatic cell transduction.
Bottom Line: The vectors deliver a tamoxifen-inducible and self-inactivating Cre recombinase, conditional bioluminescent and fluorescent proteins and an shRNA component.We also show that a variant vector expressing shRNA alters tumour growth dynamics and the histological grade associated with the inherited genotype.They should also be useful for inducing imageable tumours in organs other than the lung, provided that the inherited conditional genotype is sufficiently penetrant.
Affiliation: Department of Molecular Imaging, CRUK Cambridge Institute, University of Cambridge, UK.Show MeSH
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Mentions: To induce enhanced spontaneous lung tumours in mice, we administered LV–indLS2 to the lungs of K and KP mice by intranasal inhalation (see Materials and methods). One week later, we imaged these mice to establish the non-induced baseline levels of bioluminescence, then induced Cre function with tamoxifen and imaged according to the schedule shown in Figure 2. Increased levels of bioluminescence were evident 48 h after the first dose of tamoxifen, indicating that the construct was switching in vivo. Levels of bioluminescence continued to increase until day 17–20 post-tamoxifen, when levels returned to near baseline. The levels of bioluminescence remained low for several weeks before starting to rise again. Unambiguous bioluminescent foci then became evident in both cohorts, with levels of light increasing faster in KP than K mice, consistent with the fact that KP mice additionally lack p53 expression 24,25. The histological grade of lesions from these mouse cohorts (as summarized in Table1) was broadly consistent with the imaging data, with KP mice developing higher-grade lesions than the K mice. All of the tumours present were classified as adenomas and most were 1–2 mm in maximum dimension, with no evidence of invasion into surrounding structures. Heterogeneous regions of high-grade dysplasia, as evidenced by marked nuclear polymorphism and readily identifiable mitotic figures (indicative of low- to high-grade progression), were evident in the tumours from KP mice. A mild lymphoid hyperplasia within the lung parenchyma of some mice was also noted, but we have not determined whether this was due to tumour growth alone or whether lentiviral infection contributed to it.
Affiliation: Department of Molecular Imaging, CRUK Cambridge Institute, University of Cambridge, UK.