Prior to the advent of genetic engineering in the mouse, the rat was the model of choice for investigating the etiology of cancer. Now, recent advances in the manipulation of the rat genome, combined with a growing recognition of the physiological differences between mice and rats, have reignited interest in the rat as a model of human cancer. Two recently developed rat models, the polyposis in the rat colon (Pirc) and Kyoto Apc Delta (KAD) strains, each carry mutations in the intestinal-cancer-associated adenomatous polyposis coli (Apc) gene. In contrast to mouse models carrying Apc mutations, in which cancers develop mainly in the small intestine rather than in the colon and there is no gender bias, these rat models exhibit colonic predisposition and gender-specific susceptibility, as seen in human colon cancer. The rat also provides other experimental resources as a model organism that are not provided by the mouse: the structure of its chromosomes facilitates the analysis of genomic events, the size of its colon permits longitudinal analysis of tumor growth, and the size of biological samples from the animal facilitates multiplexed molecular analyses of the tumor and its host. Thus, the underlying biology and experimental resources of these rat models provide important avenues for investigation. We anticipate that advances in disease modeling in the rat will synergize with resources that are being developed in the mouse to provide a deeper understanding of human colon cancer.

Purpose To update the results of a clinical trial that assessed whether the angiotensin-converting enzyme inhibitor captopril was effective in mitigating chronic renal failure and pulmonary-related mortality in subjects undergoing total body irradiation (TBI) in preparation for hematopoietic stem cell transplantation (HSCT). Methods and Materials Updated records of the 55 subjects who were enrolled in this randomized controlled trial were analyzed. There were 28 on captopril and 27 on placebo. The definitions of TBI-HSCT-related chronic renal failure (and relapse) were the same as in the 2007 analysis. Pulmonary-related mortality was based on clinical or autopsy findings of pulmonary failure or infection as the primary cause of death. Follow-up data for overall and pulmonary-related mortality was supplemented by use of the National Death Index. Results The risk of TBI-HSCT-related chronic renal failure was lower in the captopril group (11% at 4 years) than in the placebo group (17% at 4 years) but this was not statistically significant (p>0.2). Analysis of mortality was greatly extended by use of the National Death Index, and no patients were lost to follow-up for reasons other than death prior to 67 months. Patient survival was higher in the captopril compared with the placebo group, but this was not statistically significant (p>0.2). The improvement in survival was influenced more by a decrease in pulmonary mortality (11% risk at 4 years in the captopril group vs. 26% in the placebo group, p=0.15) than by the decrease in chronic renal failure. There was no adverse effect on relapse risk (p=0.4). Conclusions Captopril therapy produces no detectable adverse effects when given after TBI. Captopril therapy reduces overall and pulmonary-related mortality after radiation-based HSCT and there is a trend towards mitigation of chronic renal failure.

SummaryPurpose-Chronic renal failure is an acknowledged complication of hematopoietic stem cell transplantation (HSCT) in humans. It can be caused in part by radiation injury when HSCT is preceded by sufficient total body irradiation (TBI). Studies in laboratory animals show the benefit of angiotensin converting enzyme (ACE) inhibitors in mitigation and treatment of this complication. We thus conducted a randomized controlled trial testing whether the ACE inhibitor captopril was effective in mitigating chronic renal failure after HSCT.Methods and materials-55 subjects undergoing TBI-HSCT were enrolled. Captopril, or identical placebo, was started at engraftment, and continued as tolerated until one year after HSCT.Results-The baseline serum creatinine and calculated glomerular filtration rate (GFR) did not differ between groups. The one-year serum creatinine was lower, and the GFR higher, in the captopril compared to the placebo group ( p=0.07, for GFR). Patient survival was higher in the captopril compared to the placebo group, but this was also not statistically significant (p=0.09). In study subjects who were on study drug for more than two months, the one-year calculated GFRs were 92 ml/min and 80 ml/min, for the captopril and placebo groups, respectively (p=0.1). There was no adverse effect on hematological outcome.Conclusion-We conclude that there is a trend in favor of captopril in mitigation of chronic renal failure after radiation-based HSCT.

Current screening procedures for colorectal cancer are imperfect, highly invasive and result in increased mortality rates due to low compliance. The goal of the experiments reported herein is to identify potential blood-based biomarkers indicative of early-stage intestinal cancers using the ApcMin/+ mouse model of intestinal cancer as an experimental system. Serum proteins from tumor-bearing ApcMin/+ mice were quantitatively compared to tumor-free Apc+/+ wild-type mice via in anima metabolic labeling with 14N/15N labeled Spirulina algae and an LTQ Orbitrap mass spectrometer. Out of 1116 total serum proteins quantified, this study identified 40 that were differentially expressed and correlated with the increase in intestinal neoplasms. A subset of these differentially expressed proteins underwent a secondary quantitative screen using selected reaction monitoring-mass spectrometry with stable isotope-labeled peptides. Using both quantitative techniques, we identified MGAM and COL1A1 as downregulated and ITIH3 and F5 as upregulated in serum. All but COL1A1 were similarly differentially expressed in the mRNA of neoplastic colonic tissues of ApcMin/+ mice compared to normal wild-type tissue. These differentially expressed proteins identified in the ApcMin/+ mouse model have provided a set of candidate biomarkers for future validation screens in humans.

Suppression of the renin-angiotensin system has proven efficacy for mitigation and treatment of radiation nephropathy, and it has been hypothesized that this efficacy is due to suppression of radiation-induced chronic oxidative stress. It is known that radiation exposure leads to acute oxidative stress, but direct evidence for radiation-induced chronic renal oxidative stress is sparse. We looked for evidence of oxidative stress after total-body irradiation in a rat model, focusing on the period before there is physiologically significant renal damage. No statistically significant increase in urinary 8-isoprostane (a marker of lipid peroxidation) or carbonylated proteins (a marker of protein oxidation) was found over the first 42 days after irradiation, while a small but statistically significant increase in urinary 8-hydroxydeoxy-guanosine (a marker of DNA oxidation) was detected at 35-55 days. When we examined renal tissue from these animals, we found no significant increase in either DNA or protein oxidation products over the first 89 days after irradiation. Using five different standard methods for detecting oxidative stress in vivo, we found no definitive evidence for radiationinduced renal chronic oxidative stress. If chronic oxidative stress is part of the pathogenesis of radiation nephropathy, it does not leave widespread or easily detectable evidence behind.

The purpose of this study was to evaluate in an animal model the safety and efficacy of dietary supplementation with high doses of selenium for the mitigation of the type of radiation injury that might be sustained during a nuclear accident or an act of radiological terrorism. Age-matched male rats were exposed to 10 Gy (single dose) of total-body irradiation (TBI) followed by a syngeneic bone marrow transplant, then randomized to standard drinking water or drinking water supplemented with sodium selenite or seleno-L-methionine. At 21 weeks after TBI, most rats on standard drinking water had severe renal failure with a mean blood urea nitrogen (BUN) level of 124 ± 29 mg/dl (geometric mean ± SE) whereas rats on selenium-supplemented drinking water (100 μg/day) had a mean BUN level of 67 ± 12 mg/dl. The mitigating effect of selenium was confirmed by histopathological analyses. None of the animals on high-dose selenium showed signs of selenium toxicity. Our results suggest that dietary supplementation with high-dose selenium may provide a safe, effective and practical way to mitigate radiation injury to kidneys.

The development of noninvasive methods for early detection of colon cancer is critical for the successful management of this disease. Using a targeted quantitative proteomics technique, we assessed the ability of 12 serum proteins to detect the presence of colonic polyps in the Apc Pirc/þ rat model of familial colon cancer. Serum protein candidates were selected from gene transcripts upregulated in colonic tumors of Apc Pirc/þ rats and from a prior study of serum proteins differentially expressed in mice carrying intestinal adenomas. Proteins were quantified at early stages of polyp formation in a rat cohort monitored longitudinally by colonoscopy over a period of 75 days. Of the 12 proteins monitored at three distinct time points, seven showed differential expression in at least one time point in the serum from Apc Pirc/þ rats compared with wild-type rats. Tumor multiplicity correlated with protein expression changes, and most tumors grew during the study. EGFR, LRG1, ITIH4, and F5 displayed the most robust tumor-associated protein expression changes over time. Receiver operator characteristic analysis using these four proteins resulted in a sensitivity of 100%, a specificity of 80%, and an area under the curve of 0.93 at 135 days of age, when the Pirc rats bore an average of 19 tumors in the colon and seven in the small intestine. The results of this study demonstrate that the quantitative analysis of a panel of serum proteins can detect the presence of early intestinal tumors in a rat model, and provides support for future measurements in humans. Cancer Prev Res; 7(11); 1160-9. Ó2014 AACR.

Studies of tumors from human familial adenomatous polyposis, sporadic colon cancer, and mouse and rat models of intestinal cancer indicate that the majority of early adenomas develop through loss of normal function of the Adenomatous polyposis coli (APC) gene. In murine models of familial adenomatous polyposis, specifically the multiple intestinal neoplasia mouse (Min) and the polyposis in the rat colon (Pirc) rat, most adenomas have lost their WT copy of the Apc gene through loss of heterozygosity by homologous somatic recombination. We report that large colonic adenomas in the Pirc rat have no detectable copy number losses or gains in genomic material and that most tumors lose heterozygosity only on the short arm of chromosome 18. Examination of early mouse and rat tumors indicates that a substantial subset of tumors shows maintenance of heterozygosity of Apc in genomic DNA, apparently violating Knudson's two-hit hypothesis. Sequencing of the Apc gene in a sampling of rat tumors failed to find secondary mutations in the majority of tumors that maintained heterozygosity of Apc in genomic DNA. Using quantitative allele-specific assays of Apc cDNA, we discovered two neoplastic pathways. One class of tumors maintains heterozygosity of Apc Min/+ or Apc Pirc/+ RNA expression and may involve haploinsufficiency for Apc function. Another class of tumors exhibits highly biased monoallelic expression of the mutant Apc allele, providing evidence for a stochastic or random process of monoallelic epigenetic silencing of the tumor suppressor gene Apc.epigenetics | genomic stability | loss of imprinting | X-inactivation