ABSTRACT
Antibodies to cancer antigens can often be detected in the sera of patients, although the mechanism of the underlying humoral immune response is poorly understood. Using immunoscreening of tumor-derived cDNA expression libraries (SEREX), we identified human histone deacetylase 3 (HDAC3) as serologically defined antigen in colon cancer. Closely related HDAC1 and HDAC2 do not elicit humoral response in colon cancer patients. We show that the C-terminal region of HDAC3 protein lacking the homology to other Class I HDAC contains at least 3 distinct B-cell epitopes that are recognized by the serum antibodies. HDAC3 in combination with other SEREX antigens may become a useful molecular biomarker with diagnostic or prognostic value for a subset of colon cancer patients.