Abstract: Objective The aim of this study was to investigate the effect of decitabine combined with cisplatin in the treatment of colorectal cancer and its effect on the structure of intestinal flora.Methods In the study,a mouse colorectal cancer xenograft model was established,and the changes in tumor volume and overall survival of mice after the treatment with decitabine,cisplatin,and decitabine combined with cisplatin were measured;the changes of ABCB1 and MYC gene expression in transplanted tumor tissue from mice treated with decitabine,cisplatin,and decitabine combined with cisplatin were detected;fecal samples of mice were collected,the changes of intestinal flora structure were compared in mouse models by Miseq sequencing.Results The combined use of decitabine and cisplatin could reduce the tumor growth rate and prolong the overall survival time of mouse transplanted tumor models;the combined use could reduce the expression of ABCB1 and MYC genes in a model model.The result of Miseq sequencing showed that the intestinal flora of mice changed significantly after different treatments.The detection rates of Escherichia coli,Enterococcus faecalis and other pathogenic bacteria were significantly higher in the stool of colorectal cancer xenograft mouse models.Conclusion Decitabine combined with cisplatin in the treatment of colorectal cancer can effectively inhibit the growth of tumor and prolong the overall survival time.The larger proportion of pathogenic bacteria in the intestinal track of mouse models may be the important reason for the development of colorectal diseases.When using cisplatin to treat colorectal cancer,it also needs to be combined with intestinal flora conditioning drugs for combined treatment.

Key words: Colorectal cancer, Flora, Decitabine, Cisplatin, Drug combination