Expressão imunohistoquímica de P53 e Ki-67 na carcinogênese esofágica induzida pela dietilnitrosamina: modelo experimental / Immunohistochemical expression of P53 and Ki-67 in diethylnitrosamine-induced carcinomas esophageal: experimental model

OBJETIVO: Avaliar a expressão imunohistoquímica de p53 e ki-67 na carcinogênese esofágica induzida quimicamente através do uso de dietilnitrosamina, em um grupo de 100 camundongos fêmeas. MÉTODOS: O estudo experimental foi realizado com quatro grupos de animais, onde os grupos I e II foram considerados controles, sendo diferenciados por gavagem esofágica, uma vez semana, com água fria (temperatura ambiente) ou quente (60º-70ºC). E os grupos III e IV foram considerados estudos, os quais receberam dietilnitrosamina por três dias consecutivos semanalmente, também sendo diferenciados por gavagem, uma vez por semana, com água fria ou quente. O estudo apresentou datas progressivas de sacrifícios com coleta de peças esofágicas, que iniciava aos 30 dias de experimento e terminava aos 150 dias. Demonstrou-se que não houve diferença na incidência tumoral quando foi acrescida a variável temperatura da água; provavelmente devido ao episódio único semanal que era adicionado ao animal em experimentação. RESULTADOS: A análise imunohistoquímica do p53 não evidenciou diferença estatística durante a evolução da carcinogênese até 150 dias, porém quando analisado a relação com alterações patológicas demonstra-se que apresenta significância em relação à patologia baixo grau de displasia, alto grau e carcinoma. CONCLUSÃO: A análise imunohistoquímica do ki-67 demonstrou diferença estatística durante a evolução da carcinogênese a partir do dia 120 de experimento e quando analisada a relação com alterações patológicas demonstrou-se que apresenta significância também em relação à lesão intraepitelial de alto grau e carcinoma.

OBJECTIVE:To evaluate the expression of P53 and Ki-67 during esophageal diethylnitrosamine (DEN)-induced carcinogenesis in 100 mice by immunohistochemistry. METHODS: The animals were assigned to 4 groups, receiving water and food ad libitum. Control groups I and II received weekly esophageal gavage with cold (room temperature) or hot (60-70ºC) water, respectively. Experimental groups III and IV were treated with DEN for 3 consecutive days during the week, and one weekly gavage as above. The mice were sacrificed in different periods from day 30 to day 150 after the beginning of the experiment, for collection of esophageal samples which were then submitted to microscopic and immunohistochemical analyses. The temperature of the water administered by gavage was not related to the frequency of esophageal tumors. RESULTS:The expression of Ki-67 was significantly higher in high-grade intraepithelial lesion (I.L.), and the expression of P53 was also higher in low-grade I.L. CONCLUSION:The results emphasize the direct relationship of the carcinogenic process with early cell alterations detected by immunohistochemistry.

Lack of promoting effects of phenobarbital at low dose on diethylnitrosamine-induced hepatocarcinogenesis in TGF-alpha transgenic mice.

Phenobarbital (PB), a rodent non-genotoxic carcinogen, showed hormesis, biphasic effects on rat liver carcinogenesis. To test the hypothesis that the hormesis earlier observed for PB induced hepatocarcinogenesis might also exist in the TGF-alpha transgenic mice model, one which is highly susceptible to carcinogenesis, the carcinogenic or promotion effects of a wide range of phenobarbital (PB) concentrations were investigated. Two weeks after a single i.p. dose of 5 mg /kg bw of diethylnitrosamine (DEN) to 15 day old mice, animals were treated with diet containing PB at doses of 0, 2, 15 or 500 ppm. The incidence and multiplicity of tumors, including hepatocellular adenomas and carcinomas, were significantly increased by the high dose of PB, but no significant difference among the groups receiving 2 and 15 ppm for liver tumors when compared to DEN alone group. The proliferating cell nuclear antigen indices for liver tumors and surrounding hepatocytes in high dose PB treated mice were significantly increased, but no change was noted at the lower doses. The total cytochrome P450 content in the liver was also elevated by 500 ppm of PB, while hepatic 8-OHdG levels demonstrated no significant change. In conclusion, PB at high dose enhances DEN-induced hepatocarcinogenesis in TGF-alpha transgenic mice, but low doses lack any significant effects. One possible mechanism of phenobarbital carcinogenicity might be influenced by cytochrome P450 system exhibiting a strong promoting activity for liver of mice.

Caffeine, quercetin and alizarin stimulate the exhalation of metabolic products of [14C]-N-nitrosodiethylamine in mice.

Naturally occurring plant products belonging to different chemical classes namely alizarin, an anthraquinone, caffeine, a methylxanthine derivative and quercetin, a flavonol were studied for their effect on elimination of metabolites of [14C]-N-nitrosodiethylamine (14C-NDEA) through respiration in mice. Treatment with caffeine, quercetin and alizarin at doses of 200, 9 and 9 microg/ml respectively, in drinking water enhanced the exhalation of 14CO2, one of the major end products of NDEA metabolism. Radioactive CO2 exhaled in 60 min increased by 2, 1.61 and 1.4-folds in animals treated with caffeine, quercetin and alizarin for 8 weeks respectively. This increase in exhalation in caffeine-treated animals was achieved even in 2 weeks. These compounds had no adverse effects on the absorption of radioactive NDEA from the gut of the animals as shape and time of 14CO2 peak was similar in i.p. and orally administered [14C-NDEA]. Increased detoxification/elimination of the carcinogen could be one of the mechanisms for the anticarcinogenic properties of these phytochemicals in lung tumorigenesis induced by orally administered NDEA.