Down-regulation of CD3zeta is a breast cancer biomarker associated with immune suppression.

This work was done to establish a correlation between serum protein expression profiles and breast cancer. A high-density antibody microarray was used to identify serum protein expression profiles. Proteins up- or down-regulated by 2-fold compared with normal controls were used for hierarchical clustering analysis. ELISA and immunohistochemistry were used for validation of protein array data. The CD3zeta chain was one of the down-regulated molecules identified by the antibody array analysis and confirmed by ELISA and immunohistochemistry. The mean CD3zeta levels in breast cancer and in normal control were 119±23 and 156±35 ng/ml, respectively. The AUC (area under the curve) of CD3zeta was 0.837±0.057. Forty-one out of 65 breast cancer cases (63.08%) showed reduced CD3zeta expression on tumour-infiltrating lymphocytes by immunohistochemistry. This is the first report describing down-regulation of CD3zeta expression on breast cancer for the Chinese population and suggests that an immunosuppressive status plays an important role in breast cancer progression.