Studies On Chemopreventive Effects Of Curcumin On Hepatocarcinogenesis In Rats Induced By Nitrosamine

Backgroud/Objectives: The development of human cancer is a long-time and multiphase process, the scope of chemoprevention encompasses cohorts at all phases of this process梖rom healthy subjects at normal risk, to populations at intermediate risk resulting from environmental and lifestyle factors, genetic predisposition, and precancerous lesions, and then to the patients at high risk for second malignancy. So they expect to get chemopreventive drugs with safety and efficiency. Diet-derived chemopreventive agents are highly interested because of their safety and compliance. Curcumin is dominating active components of Curcuma longa and can be used as spice and edible pigment. Simultaneously, curcumin possess widespread pharmacological effect, such as antiinflammation, antioxidation, anticoagulation et al. Recently, curcumin is attached importance on account of its anticancer properties. Understanding possible molecular targets is very important to elucidate mechanisms for curoumin chemoprevention. Gene chip allows monitoring the expression of thousands or tens of thousands genes simultaneously in one hybridization experiment. Employing this technique, detection of differentially expressed genes regulated by curcumin is greatly facilitated. The thesis aimed to observe the inhibition effects of curcumin on hepatocarcinogenesis induced by nitrosamine on Wistar rats and to evaluate chemopreventive effect of curcumin on hepatocarcingenesis, and to investigate mechanisms for chemoprevention by curcumin with possible molecular targets by gene chip. It is focused on the questions as follows. 1) To observe the inhibition effects of diet containing 2% turmeric powder on hepatocarcinogenesis induced by nitrosamine on Wistar rats. 2) To investigate the intermediate biomarker that evaluates the chemopreventive effects of curcumin on hepatocarcinogenesis in order to be used in clinical research. 3) To discover the possible molecular targets by gene chip in order to elucidate the mechanisms of chemoprevention by curcumin. Methods 1) Wistar rats were given a single i.p. injection of 40mg/kg body weight N-diethylnitrosamine(DEN) at age 6 weeks. After 4 weeks, rats received l2Oppm N-nitrosomorpholine in drinking water for 28 weeks. The curcumin A group started eating 2% turmeric powder-containing diet 7 days before DEN injection until execution. The rats in curcumin B group were given 2% turmeric powder-containing diet until hepatocellular carcinoma had been induced at 24th week. Then, the rats in experimental group and curcumin A group were sacrificed at 16th, 20th and 24th week to examine the development of hepatocellular carcinoma. At the 32nd week, all rats were executed to compare the curcumin group with the experimental group on incidence, multiplicity and metastasis of hepatocarcinoma. The changes of hepatic tissues in morphology were observed through hematoxylin-eosin (HE) staining.. 2) Proliferation index displayed by PCNA through immunohistochemistry and apoptotic index revealed by TUNEL are used to evaluate the chemopreveritive effects on curcumin for every stage of hepatocarcinogenesis induced by nitrosamine, and to set up a discriminant function to develop discriminant analysis in order to determine the preventive effects using intermedial biomarker at early-middle stage. 3) The hepatic tissue specimens come from...