Endometrial cancer patients have high affinity antibodies for estrogen metabolite-receptor aggregate: A potential biomarker for EC

Abstract

Aim: Elevated levels of 16α-hydroxyestrone (16α-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 16α-OHE₁ -ERα 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 16α-OHE₁ -ERα 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 16α-OHE₁ -ERα compared to ERα (P < 0.05) or 16α-OHE₁ (P < 0.001). The relative affinity of EC IgG was 1.49 × 10^-7 M, 1.34 × 10^-6 M and 1.13 × 10^-6 M for 16α-OHE₁ -ERα, ERα and 16α-OHE₁ , respectively. Several factors, such as obesity, postmenopausal status, use of hormonal therapy, ER and progesterone receptor (PR) status, low 2-OHE₁ /16α-OHE₁ ratio, chemotherapy and hypertension, augment the production of antibodies against 16α-OHE₁ -ERα in EC patients.

Conclusion: 16α-OHE₁ -ERα 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 16α-OHE₁ -ERα in the sera of these EC patients.

Keywords: 16α-hydroxyestrone; ELISA; antibodies; endometrial cancer; estrogen receptor.