Amphiphysin, a neuronal protein first identified in chicken synaptic membranes, is the autoantigen of Stiff-Man Syndrome (SMS) associated with breast cancer. Patient autoantibodies have a distinct pattern of reactivity with amphiphysin, and the dominant autoepitope is located in its C-terminal region, which contains an SH3 domain (1). Amphiphysin is expressed in many neurons, certain endocrine cell types, and spermatocytes (2). study suggests a link between amphiphysin I expression in cancer and amphiphysin I autoimmunity. The enhanced expression of amphiphysin I in some forms of cancer supports the hypothesis that amphiphysin family members may play a role in the biology of cancer cells (3).
