The study is expected to guide the clinical application of folic acid and to identify the mechanism of folic acid in a microarray AP26113 gene expression profile. Materials and methods Ethics Statement Our study had been approved by Animal Care and Use Committee of Shanghai Jiao-Tong University School of Medicine Ren-Ji Hospital, Shanghai, China (approval ID: 2007-036. All animal procedures were performed according to guidelines developed by

the China Council on Animal Care and protocol approved by Shanghai Jiao-Tong University School of Medicine Ren-Ji Hospital, Shanghai, China. Chemicals 1, 2-Dimethylhydrazine (DMH) and Folic acid (FA, F8758) were obtained from Sigma Chemical Co. (St. Louis, MO, USA). The PH value of DMH is adjusted with NaHCO3 to 6.5-7.0. DMH was dissolved with Normal saline and Folic BMN 673 concentration Acid with drinking water. Experimental animals 130 females, 4 weeks old ICR mice (weight, 18-20 g;

grade, specific pathogen-free (SPF)) were bought from the Chinese Academy of Sciences (Shanghai, China). The mice were raised at constant temperature of 22°C with a relative humidity of 60% and C646 order 12-hour light/dark cycles; they were supplied a standard laboratory diet and drinking water. These 130 mice were randomly divided into 7 groups (Figure 1): NS group = 20 (Subcutaneous injection of physiological saline); DMH1 group = 20(Subcutaneous injection of DMH for 12 weeks); DMH group = 20 (Subcutaneous injection

of DMH for 24 weeks); Cfa (control Folic Acid) = 10 (only intragastric administration of folic acid without DMH injection; FA1 = 20 (intragastric administration of folic acid with DMH injection for early 12 weeks); FA2 = 20(intragastric administration of folic acid with DMH injection for later 12 weeks); FA3 = 20 (intragastric administration of folic acid with DMH injection for 24 weeks). DMH was given subcutaneous injection once a week at the dosage of 20 mg/kg and folic acid was given by intragastric administration twice a week. All mice were weighted Rutecarpine once a week. At the 12th weeks after DMH injection, 10 of NS and groups of DMH1, FA1 were killed and the conditions of organs were recorded. The mass number and size were assessed using a micrometer. Some fresh colon and rectal tissues were maintained immediately in liquid nitrogen, and others include liver or gastric tissues were fixed in formalin solution and embedded in paraffin blocks for pathological analysis. At the end of 24th weeks, all remaining mice were killed using the same methods. Figure 1 Groups of this study.