Abstract
Aim Elevated levels of 16 alpha-hydroxyestrone (16 alpha-OHE1) have been described in endometrial cancer (EC) and estrogen receptors (ER) expressed in endometrial tissue, but research on their combined role is lacking. We aimed to investigate the affinity and binding specificity of EC antibodies against the 16 alpha-OHE1-ER alpha aggregate in the serum of EC patients. Specificities of EC antibodies were also evaluated according to various clinical characteristics found in these cancer patients.
Methods The binding specificity and affinity of EC antibodies against 16 alpha-OHE1-ER alpha in the serum of 120 EC patients were evaluated by direct binding and competition ELISA and quantitative precipitation titration. Binding of EC antibodies was also determined according to various clinical characteristics in EC patients through competition ELISA.
Results Antibodies from EC patients demonstrated high recognition of 16 alpha-OHE1-ER alpha compared to ER alpha (P < 0.05) or 16 alpha-OHE1(P < 0.001). The relative affinity of EC IgG was 1.49 x 10(-7) M, 1.34 x 10(-6) M and 1.13 x 10(-6) M for 16 alpha-OHE1-ER alpha, ER alpha and 16 alpha-OHE1, respectively. Several factors, such as obesity, postmenopausal status, use of hormonal therapy, ER and progesterone receptor (PR) status, low 2-OHE1/16 alpha-OHE(1)ratio, chemotherapy and hypertension, augment the production of antibodies against 16 alpha-OHE1-ER alpha in EC patients.
Conclusion 16 alpha-OHE1-ER alpha is a high-affinity antigen for EC antibodies in the serum of EC patients and might function as a biomarker for this disease. Furthermore, several factors enhanced the production of antibodies against 16 alpha-OHE1-ER alpha in the sera of these EC patients.