Since the production of tumor-associated antibodies (TAAs) is considered to be a humoral immune response in cancer patients, serum autoantibodies may be detected even in patients with early stage tumors. Seventeen recombinant proteins with tags in Escherichia coli (p53, RalA, p90, NY-ESO-1, HSP70, c-myc, galectin-1, Sui1, KN-HN-1, HSP40, PrxVI, p62, cyclin B1, HCC-22-5, annexin II, HCA25a, and HER2) were applied as capturing antigens in sandwich ELISA to measure serum IgG levels. Sera from 73

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... althy donors and 386 patients with breast cancer, including 182 stage 0/I patients, were evaluated by using cutoff values for each TAA equal to the mean +3 SDs of the serum levels of healthy controls. The positive TAA rates were relatively high for p53 (10%) and RalA (10%). The positive rates of all TAAs of stage 0/I were similar to those of all patients. Even in the stage 0/I patients, 24% showed that two or more TAAs were positive, and the positive rate of a five-TAA combination assay was 37%. The positivity rate was significantly higher for the non-luminal type than for the luminal type (p = 0.003). Logistic analysis showed that seropositivity (positive for one or more TAAs) in breast cancer patients was independent from any TNM factor or disease stage and was significantly associated with histological grade in the multivariate analysis (p = 0.007). TAAs in breast cancer patients may be useful for early detection. However, seropositivity of breast cancer reflects the tumor characteristics but not the disease stage.