ObjectiveTo establish the co-culture model of mice's early embryo and tumor cells in Vitro to observe the embryonic development and biologic behavior of tumor cells in the same microenvironment and discuss their interaction. MethodsWe acquired 2-cell embryos from mice, and then co-cultured them with tumor cell lines of mice in Vitro. We observed the development of embryos in Vitro and the rates of 4-cell embryos, morula and blastocyst formation. The transwell chamber was used for culture. Methylthiazolyldiphenyl-tetrazolium method was used to test the proliferative activity of tumor cells, while the flow cytometry was used to test its apoptosis. The interaction of co-cultured embryos and tumor cells was analyzed by propidium iodide staining and immunohistochemical technique. ResultsThe co-cultured 2-cell embryos could continue surviving and developing. The rates of 4-cell embryos, morula and blastocyst formation increased significantly in the co-cultured group (P<0.05). There was no significant difference in the proliferative activity and apoptosis of tumor cells between the co-cultured group and the control group (P>0.05). Tumor-free ring formed between the trophoblast and tumor cells. We could observe tumor cells stacked around the tumor-free ring. However, no difference in expression of proliferating cell nuclear antigen and B-cell lymphoma leukemia-2 was observed in tumor cells stacking around the tumor-free ring compared with those elsewhere. ConclusionThe development of 2-cell embryos is enhanced in the co-culture model. The proliferative activity and apoptosis of tumor cells are not affected in this model. A tumor-free ring can form between trophoblast and tumor cells. However, the proliferative activity of tumor cells is not affected by this ring.