In order to induce colon cancer, the rats were given a weekly subcutaneous injection of 1,2-Dimethylhydrazine (DMH) at a dose of 20 mg/kg b.w. for five weeks. Afterwards, some of the rats ingested fish oil for either 4 weeks (DMH-FO4 group), or 17 weeks (DMH-FO17 group). The remaining rats continued without any supplementation for the same 4 weeks (DMH4 group), or 17 weeks (DMH17 group). Another two groups of rats did not receive the DMH and were given fish oil (FO17 group) or a normal diet only and considered as the control group (CN group). At the end of the experiment, the rats were sacrificed; and were subsequently subjected to biochemical and molecular biological analyses as well as histopathological examinations. The results showed increased levels of lactate dehydrogenase (LDH), malondialdehyde (MDA) and alkaline phoshatase (ALP) activities in the DMH rats compared to the control. The liver and colonic changes that were induced by DMH were significantly improved through fish oil supplementation in the DMH-FO17 group. The molecular analysis revealed that DMH treatment induced the expression alterations of genes p53, p27 and p21 and increased DNA band patterns related to cancer, while both FO17 and DMH-FO17 groups showed much better results. A histopathological examination of the DMH17 group revealed colon adenocarcinoma and several lesions in rat liver tissues. An improvement in the histopathological picture was seen in the livers and colons of groups DMH-FO17. In conclusion, the present results demonstrated the anti-carciongenic effect of herring fish oil against DMH induced colon carcinogenesis in rats. The inhibitory effect of FO was due to the modulation of elevated biochemical parameters, DNA damage, gene expression and histopathological lesions caused by DMH.
KEY-WORDS: Colorectal cancer -DMH -Fish oil -Gene expression -Rats.
INTRODUCTIONAmong the factors that contribute to the appearance of cancer, diet plays a fundamental role. Fats are the main component related to the increase in the incidence of cancerous diseases, particularly breast, prostate and colorectal cancer. Colon cancer is one of the leading causes of death in both men and women in Western countries (Parker et al., 1995;and Jemal et al., 2003) and it became the number six leading cause of cancer deaths in Egypt (WHO report, 2006). Several RESUMEN Efecto del aceite de pescado de la dieta en cáncer de colon inducido por dimetilhidrazina en ratas.Este estudio fue realizado para examinar la eficacia de la suplementación de aceite de pescado en la carcinogéne-sis de colon en ratas wistar machos. Para la inducción del cáncer de colon, las ratas fueron tratadas semanalmente con una inyección subcutánea de 1,2-dimethyl hydrazine (DMH) a una dosis de 20 mg/kg de peso durante cinco semana. A continuación, algunas ratas tomaron aceite de pescado durante 4 semanas, o durante 17 semanas (grupo DMH-FO17). Las ratas restantes continuaron sin ningún tipo de suplementación durante las mismas 4 semanas (grupo DMH4), o 17 semanas (grupo DMH17). Otros dos...