Proteins nectin-3 having the amino acid sequences represented by SEQ ID NOS: 2, 4 and 6 which are novel proteins belonging to the nectin protein family participating in the adhesion between cells
polynucleotides encoding these proteins nectin-3 and having the base sequences respectively represented by SEQ ID NOS:1, 3 and 5
recombinant vectors having these polynucleotides
and antibodies against the above-described proteins nectin-3. The proteins necti n- 3 not only provide important information in clarifying the whole molecular mechanism of cell adhesion but potentially relate to the clarification of, f or example, the infiltration and metastasis mechanisms of cancer, thereby being useful in diagnosing the malignancy of cancer, developing methods of preventing and treating the same and remedies, etc. therefor.