16α-hydroxyestrone and its receptor complex: high affinity antigen for antibodies from prostate cancer patients

Background and objectives: Elevated levels of 16α-hydroxyestrone (16α-OHE1) have been linked to increased risk of prostate cancer (PC) and estrogen receptor (ER) had been expressed in prostate tissue but the combined effect of 16α-OHE1 and ER (α) is lacking. We investigated the binding specificity of antibodies from PC with 16α-OHE1-ER complex in the sera from PC patients.Materials and methods: The antibodies in the serum from 60 PC patients and 40 control subjects were evaluated from ELISA (direct binding and competition) and quantitative precipitin titration. Competition ELISA was also used to estimates 16α-OHE1 concentration and 2-hydroxyestrone (2-OHE1)/16α-OHE1 ratio in PC patients.Results: Antibodies from PC patients demonstrate high binding to 16α-OHE1-ER in comparison to ER (p < 0.05) or 16α-OHE1 (p < 0.001). The relative affinity of PC IgG was found to be high for 16α-OHE1-ER (1.19 × 10−7 M) as compared to ER (1.45 × 10−6 M) or 16α-OHE1 (1.13 × 10−6 M).Conclusion: High affinity of PC IgG with 16α-OHE1-ER might explain the possible antigenic role and 16α-OHE1-ER acted as high affinity antigen for antibodies from PC. The interaction between 16α-OHE1 and ER makes a complex in the prostate tissues and this may generate antibodies against this complex in the cancer patients.