Research progress in establishment of N-methyl-N'-nitro-N-nitroso-guanidine-induced rat model of Precancerous lesion of gastric cancer / 中国中药杂志

Gastric cancer(GC), one of the most common malignancies worldwide, seriously threatens human health due to its high morbidity and mortality. Precancerous lesion of gastric cancer(PLGC) is a critical stage for preventing the occurrence of gastric cancer, and PLGC therapy has frequently been investigated in clinical research. Exploring the proper animal modeling methods is necessary since animal experiment acts as the main avenue of the research on GC treatment. At present, N-methyl-N'-nitro-N-nitroso-guanidine(MNNG) serves as a common chemical inducer for the rat model of GC and PLGC. In this study, MNNG-based methods for modeling PLGC rats in related papers were summarized, and the applications and effects of these methods were demonstrated by examples. Additionally, the advantages, disadvantages, and precautions of various modeling methods were briefly reviewed, and the experience of this research group in exploring modeling methods was shared. This study is expected to provide a reference for the establishment of MNNG-induced PLGC animal model, and a model support for the following studies on PLGC.

Neoplastic transformation of human osteoblast-like cell line HOS TE85 / 第三军医大学学报

Objective To establish human osteoblast-like cell lines TE85 model of neoplastic transformation for exploring molecular mechanism in canceration process of osteosarcoma.Methods HOS TE85 cells were treated by MNNG(initiated factor) and TPA(promotor).The malignancy of transformed cells was identified by observing the cell form,colony forming frequency on soft agar and tumorigenesis in nude mice.Results Continuous passage after induction of neoplastic transformation led to the formation of a few paramorph foci that exhibited an extensively random orientation.The agglomeration in experiment group was more than that in control group.As compared with that of negative control cells,colony formation efficiency of transformed cells in semisolid agar showed a significant increase and the transformed cells could form tumor subcutaneously in the nude mice.The tumors were a poorly differentiated osteosarcoma confirmed by histopathological examination.Conclusion Simulating the process of malignant transformation of human cells,we establish neoplastic transformation of human osteoblast-like cell lines TE85 model.

INDUCTION OF INTESTINAL METAPLASIA AND DYSPLASIA IN MONGOLIAN GERBILS INFECTED WITH HELICOBACTER PYLORI / 解放军医学杂志

Objective Using a model of H.pylori infected Mongolian gerbil , we observed the effect of H.pylori and N methyl N’ nitro N nitrosoguanidine (MNNG) on gastric mucosa, in an attempt to clarify the potential role of vitamin C in the prevention of gastric carcinoma. Methods A total of 160 Mongolian gerbils , eight week old, were randomly divided into five groups(each 32 animals): Group A, infected with H.pylori ; Group B, infected with H.pylori followed by MNNG administration; Group C, received MNNG without H.pylori infection; Group D, infected with H pylori followed by administration of MNNG and vitamin C; Group E as control. Eight animals from each group were killed at 12, 24, 36, 48 weeks, and histopathological changes in their stomachs were examined for chronic gastritis, intestinal metaplasia, atypical hyperplasia and adenoma. Results The incidences of intestinal metaplasia and dysplasia in groups A and B were significantly higher than those in the other groups( P

Carcinogenesis of Murine Astrocytes in Culture

Astrocytes play important roles in normal brain development and the physiological processes. In particular, 30% of the brain volume consists of astrocytes, and they are the primary target cell in the brain for cellular injuries from chemical exposures. The present study attempts to establish an immortalized murine astrocyte cell line to study the mechanisms of chemical-induced carcinogenesis of astrocytes. Primary astrocytes isolated from mice were transfected with plasmid carrying the SV40 T antigen. Clonal cells obtained after G418 selection were continuously subcultured to establish an immortalized astrocyte cell line. The cell line was positive on GFAP expression and was sensitive to exposure to such chemicals as MNNG. Cells were treated with MNNG for 5 days, with doses ranging from 0.001ug/ml to 1ug/ml. Dose-dependent cellular transformations of astrocytes were observed. Treatments at 0.01ug/ml showed the most distinct characteristics of neoplastic transformation. Subsequent treatment with TPA produced higher levels of neoplastic cell transformation than MNNG treatment alone, as evidenced by increases of saturation density, soft-agar colony formation and cell aggregation. Promotional effects of TPA on cell transformation was further demonstrated by the shortening duration of foci appearance. Addition of hydrocortisone to the culture media resulted in further promotion of cell transformation in astrocytes treated with MNNG and TPA, suggesting that glucocortocoid also plays a role in the promotion of chemical-induced astrocyte transformation. The present study demonstrates that astrocytes are susceptible to chemical-induced carcinogenicity and subject to mechanisms of multistage carcinogenesis. Analysis of MNNG-transformed astrocytes showed that, while the expression of TGF-beta was decreased, expression of GFAP, IL-1betaand fibronectin were increased. The results suggest that these factors are associated with mechanisms of MNNG-induced astrocyte transformation and may be used as potential candidates for biomarkers representing astrocyte-related tumors and cell toxicities. The study showed scientific evidence that growth factors, cytokine and the extracellular matrix are involved in processes of chemical-induced transformation of astrocytes. In addition, the present work provided an excellent opportunity to develop an immortalized astrocyte cell line that can be used for studying mechanisms of astrocyte-related diseases.

Ossification of the N-methyl-N'-nitro-N-nitrosoguanidine-induced small intestine adenocarcinomas in rats

Eighty rats out of 233 developed malignant tumors in the stomach and small intestine by administration of 100 micrograms/ml N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water for 28 weeks. Fifteen lesions (30%) among the 50 small intestinal carcinomas showed ossification in the tumor, while none in the sarcomas (12 lesions) or gastric adenocarcinomas (59 lesions) showed ossification. Multifocal heterotopic bone formation was found within stroma in close approximation to the neoplastic glands. The islands of bone trabeculae were covered by osteoblast-like cells, and abundant fibroblasts in loose stroma gathered around the bony islands which enclosed osteocytes in lacunae. Neither osteoclast nor cartilage was identified. In 5 cases, ossification was extensive, which comprised the major portion of the stroma. In contrast, intraluminal calcification without ossified foci were occasionally seen in the gastric carcinoma. Ossification of the intestinal tumors correlated to the degree of mucin content (p<0.05, chi square with Yates' correction), degree of neutrophilic infiltration (p<0.05), and size of the tumor (p<0.1). (The average size of the ossified tumor was 21.5 +/- 4.0 mm, while that of nonossified tumors was 12.5 +/- 1.9 mm). The degree of tumoral necrosis, desmoplasia or depth of invasion did not seem to be related to the ossification of the tumor. The ossification rate of this experimental model was much higher than in human cases. Various histologic alterations, such as mucin leakage, inflammatory cell infiltration, necrosis and/or fibrosis, which might be caused by continuous stimulation of the strong carcinogen, may play some role in the ossification of experimental tumors.

Effect of MNNG on Ornithine Decarboxylase Activity in Cells from Adult Schistosoma japonicum / 中国寄生虫学与寄生虫病杂志

Objective To observe the change of ornithine decarboxylase(ODC) activity in cells from adult Schistosoma japonicum after the cells were treated with N\|Methyl\|N\|Nitro\|N\|Nitrosoguanidine (MNNG). Methods The cells were treated with MNNG at a concentration of 3 ?g/ml for 48 hours after the cells being incubated for one week. The cells were then cultured with RPMI\|1640 containing 10% calf serum. ODC activity was detected with spectrophotography. Results ODC activity rose significantly in two to three weeks after the cells were treated with MNNG. Conclusion There was ODC activity in cells from adult S.japonicum and MNNG has an effect to reinforce ODC activity in the cells.

EFFECT OF Na_2SeO_3 ON EXPERIMENTAL CARCINOGENESIS OF STOMACH AND ON p53 AND p16 EXPRESSION / 解剖学报

Objective To study the effect of Na-2SeO-3 on experimental carcinogenesis of stomach and on p53 and p16 expression. Methods Weaning male Wistar rats were divided into four groups randomly:high selenium group(4mg/L),low selenium(2mg/L)group,experiment control group and normal control group.Wistar rat gastric cancer was induced by N-methyl-N′-nitro-N-nitrosoguanidine(MNNG,20mg/kg)given daily for 10days.Na 2SeO 3 was given by piped drinking before one week of MNNG administration.Rats were killed at the 43th week.The surface characters of gastric mucosa were observed with noked eyes.Histopathologic changes were observed by methods of HE staining and Alcian Blue Periodic acid Schiff reaction(AB-PAS).Changes of p53 and p16 were detected by SP immunohistochemical method.The immunohistochemical results were quantitatively analysed by image analysis.Statistical analysis was taken by SPSS. Results Dietary Na-2SeO-3(2mg/L,4mg/L)aggravated gastric erosion and hemorrhage and promoted intestinal metaphasia of gastric cancer (P0.05).Conclusion These results suggest that dietary Na-2SeO-3 by piped drinking might not decrease incidence of Wistar rat gastric cancer induced by MNNG.The mechanism may be associated with the mutations of p53 and abnormal expression of p16 gene.