Since the variation of VPAC1 expression is always correlated with the occurrence and development of diseases such as tumor and immune disorders, the structure-activity-relation study of VPAC1 not only help to explain the physiological and pathological functions of VPAC1, but also provide the research basis for the drug screening and development targeting VPAC1 against tumors and autoimmune disorders. This evidence concerns the gene VIPR1 and immune system disorder.