Abstract: The invention relates to metastin derivatives represented by the formula: X-AA1-AA2-AA3-AA4-Z (I), or a salt thereof, or a pro-drug thereof, which have cancer metastatis suppressing activity and cancer proliferation suppressing activity. The invention also relates to the use of these derivatives as drugs for preventing or treating cancers.

Abstract: Screening of the autoantibodies and autoantigens which are specific to Sjögren's syndrome, particularly primary Sjögren's syndrome, and provision of a prophylactic and therapeutic drug for Sjögren's syndrome, particularly primary Sjögren's syndrome, and a highly sensitive diagnostic agent for Sjögren's syndrome. The &agr;-fodrin or &agr;-fodrin fragment of the invention is an antigen to the autoantibodies specifically found in Sjögren's syndrome and this autoantigen finds application as a prophylactic and therapeutic drug for autoimmune diseases, particularly Sjögren's syndrome, or a diagnostic agent for such diseases.