Cancer and embryo expression protein 65(CEP65) specifically reacted with Mab3H11, which can bind specifically to different cancer cells from different tissues. Northern blot and RT-PCR showed that the mRNA of CEP65 was extensively distributed in embryonic tissue and different cancerous tissues, but not in corresponding normal tissues. In order to study the function of CEP65 in tumor development, using the yeast two-hybrid system, with CEP65 as a bait, a placenta cDNA expression library was screened, and fourteen positive clones was isolated in yeast from 5.2×10⁶ clones. To ascertain the interaction, the 51st clone which interacted more intensive with CEP65 in yea was selected to do GST pull-down assay with CEP65. The result indicated that CEP65 also interacted with the 51st clone in vitro. Bioinformatics analysis showed the interaction between CEP65 and the 51st clone maybe regulate the cell differentiation and proliferation by WW domain or protein kinase C.