title: Quantitative analysis of the growth kinetics of chemically induced mouse liver tumors by magnetic resonance imaging.
abstract: Noninvasive methods for the early detection of tumor onset and progression in rodent liver would be of high value for pharmaceutical and chemical industry and would, at the same time, foster one of the 3 Rs (replacement, reduction, refinement) by reducing the number of animals in the bioassay. We have induced liver tumors in mice by single injection of diethylnitrosamine (DEN) either in 2-week- (experiment 1) or 6-week-old (experiment 2) male C3H mice. In the latter, mice were also chronically treated with 0.05% phenobarbital in diet according to an initiation/promotion protocol. Starting at 16 weeks after DEN injection (18 weeks after DEN in experiment 2), mice were routinely scanned by noninvasive magnetic resonance imaging (MRI) using a T2-weighted 3D sequence in regular intervals. Liver tumors became detectable in both experiments when they exceeded a diameter of ∼1 mm. Exponential increases in total tumor volume per liver were observed in both experiments. The onset of tumor development was similar with respect to DEN treatment. Although mice in experiment 1 had developed a mean total tumor volume of ∼100 mm³ approximately 24 weeks after DEN, it took ∼4 weeks longer to reach this tumor mass in experiment 2. Determination of time-dependent growth of individual tumors demonstrated strong tumor heterogeneity. In vivo MRI data were further correlated with tumor histology. The phenotype of tumors differed strongly between the two experiments, but our results demonstrate that tumors can be reliably detected by MRI when they exceed a certain size independent of their phenotype.
authors.affiliation: Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Department of Preclinical Imaging and Radiopharmacy, University of Tübingen, Röntgenweg 13, 72076 Tübingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmid
authors.forename: Benjamin
authors.initials: B
authors.lastname: Rignall
authors.forename: Bernd J
authors.initials: BJ
authors.lastname: Pichler
authors.forename: Michael
authors.initials: M
authors.lastname: Schwarz
mesh_terms: D023401:Animal Use Alternatives; D000818:Animals; D003043:Cocarcinogenesis; D004052:Diethylnitrosamine; D055088:Early Detection of Cancer / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008099:Liver / Q000473:pathology*; D008114:Liver Neoplasms, Experimental / Q000473:pathology*; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D010634:Phenobarbital; D015203:Reproducibility of Results; D047368:Tumor Burden
chemical_list: D004052:Diethylnitrosamine; D010634:Phenobarbital