So, analysis of antibody response in sera of breast cancer patients with tumors of different clinical and molecular characteristics showed that KRR1 and ZRF1 antigens and autoantibodies thereto are potential breast tumor markers, which could be important for creation of new antigenic/autoantibody signatures for breast tumor detection including early breast cancer diagnostics and/or for improving already existing ones. The gene discussed is KRR1; the disease is breast cancer.