Animal model in the study of colorectal carcinogenesis.
ABSTRACT Experimental animal models of neoplastic diseases are important in understanding etiological and pathophysiological processes also in humans. In order to investigate whether the mechanism of genomic instability is associated with chemically induced colorectal tumorigenesis in rat we performed the following study: One hundred and fifty Wistar rats (males 220-280 g and females 140-180 g) were used in the study. Colorectal tumors were induced by means of 15 s.c. applications (20 mg/kg) of 1,2-dimethylhydrazine (DMH). On autopsy, all intestinal lesions were assessed by histological criteria used in human pathology. Forty five tumors were found in the large intestine--30 of these in males and 15 in females, i.e. in 27% of all animals. In four animals multiple primary tumors were found. Histologically 24 tumours were adenocarcinomas, 14 signet-cell carcinoma and 7 adenomas. DNA was extracted from rat neoplastic lesions and adjoining microscopically normal tissues from the same slide and amplified by PCR, using 10 different microsatellite markers from chromosomes 1, 3, 5, 7 and 8. PCR amplicon were analyzed for microsatellite instability with non-isotopic method. In 13 adenocarcinomas (29%) microsatellite instability was found at a minimum of 1 locus. Seven tumors (15.5%) showed microsatellite instability at multiple loci. The results of our experiment suggest that genomic instability is an important molecular event in the pathophysiology of DMH induced colorectal carcinogenesis in rats.
Article: High dietary intake of sodium selenite does not affect gene mutation frequency in rat colon and liver.[show abstract] [hide abstract]
ABSTRACT: Our previous studies have shown that selenium (Se) is protective against dimethylhydrazine (DMH)-induced preneoplastic colon cancer lesions, and protection against DNA damage has been hypothesized to be one mechanism for the anticancer effect of Se. The present study was designed to determine whether dietary selenite affects somatic mutation frequency in vivo. We used the Big Blue transgenic model to evaluate the in vivo mutation frequency of the cII gene in rats fed either a Se-deficient (0 microg Se/g diet) or Se-supplemented diet (0.2 or 2 microg Se/g diet; n = 3 rats/diet in experiment 1 and n = 5 rats/group in experiment 2) and injected with DMH (25 mg/kg body weight, i.p.). There were no significant differences in body weight between the Se-deficient and Se-supplemented (0.2 or 2 microg Se/g diet) rats, but the activities of liver glutathione peroxidase and thioredoxin reductase and concentration of liver Se were significantly lower (p < 0.0001) in Se-deficient rats compared to rats supplemented with Se. We found no effect of dietary Se on liver 8-hydroxy-2'-deoxyguanosine. Gene mutation frequency was significantly lower in liver (p < 0.001) than that of colon regardless of dietary Se. However, there were no differences in gene mutation frequency in DNA from colon mucosa or liver from rats fed the Se-deficient diet compared to those fed the Se-supplemented (0.2 or 2 microg Se/g diet) diet. Although gene mutations have been implicated in the etiology of cancer, our data suggest that decreasing gene mutation is not likely a key mechanism through which dietary selenite exerts its anticancer action against DMH-induced preneoplastic colon cancer lesions in a Big Blue transgenic rat model.Biological trace element research 03/2009; 131(1):71-80. · 1.92 Impact Factor
Article: Morphological and molecular alterations in 1,2 dimethylhydrazine and azoxymethane induced colon carcinogenesis in rats.[show abstract] [hide abstract]
ABSTRACT: The dimethyhydrazine (DMH) or azoxymethane (AOM) model is a well-established, well-appreciated, and widely used model of experimental colon carcinogenesis. It has many morphological as well as molecular similarities to human sporadic colorectal cancer (CC), which are summarized and discussed in this paper. In addition, the paper combines present knowledge of morphological and molecular features in the multistep development of CC recognized in the DMH/AOM rat model. This understanding is necessary in order to accurately identify and interpret alterations that occur in the colonic mucosa when evaluating natural or pharmacological compounds in DMH/AOM rat colon carcinogenesis. The DMH/AOM model provides a wide range of options for investigating various initiating and environmental factors, the role of specific dietary and genetic factors, and therapeutic options in CC. The limitations of this model and suggested areas in which more research is required are also discussed.Journal of Biomedicine and Biotechnology 01/2011; 2011:473964. · 2.44 Impact Factor