Affinity of estrogens for human progesterone receptor A and B monomers and risk of breast cancer: a comparative molecular modeling study

Tarique N Hasan1,4, Leena Grace B2, Tariq A Masoodi3,5, Gowhar Shafi4 , Ali A. Alshatwi4, P Sivashanmugham31Department of Biotechnology, Bharathiar University, Coimbator, TN, India; 2Department of Biotechnology, V. M. K. V. College of Engineering, Salem, TN, India; 3Department of Bioinformatics, Jamal Mohammed College, Bharathidasan University, Tiruchirappalli, India; 4Molecular Cancer Biology Laboratory, Department of Food Science and Nutrition, College of Food and Agricultural Sciences; 5Department of Community Health Sciences, College of Applied Medical Sciences, King Saud University, Saudi ArabiaBackground: The human progesterone receptor (hPR) belongs to the steroid receptor family. It may be found as monomers (A and B) and or as a dimer (AB). hPR is regarded as the prognostic biomarker for breast cancer. In a cellular dimer system, AB is the dominant species in most cases. However, when a cell coexpresses all three isoforms of hPR, the complexity of the action of this receptor increases. For example, hPR A suppresses the activity of hPR B, and the ratio of hPR A to hPR B may determine the physiology of a breast tumor. Also, persistent exposure of hPRs to nonendogenous ligands is a common risk factor for breast cancer. Hence we aimed to study progesterone and some nonendogenous ligand interactions with hPRs and their molecular docking.Methods and results: A pool of steroid derivatives, namely, progesterone, cholesterol, testosterone, testolectone, estradiol, estrone, norethindrone, exemestane, and norgestrel, was used for this in silico study. Dockings were performed on AutoDock 4.2. We found that estrogens, including estradiol and estrone, had a higher affinity for hPR A and B monomers in comparison with the dimer, hPR AB, and that of the endogenous progesterone ligand. hPR A had a higher affinity to all the docked ligands than hPR B.Conclusion: This study suggests that the exposure of estrogens to hPR A as well as hPR B, and more particularly to hPR A alone, is a risk factor for breast cancer.Keywords: human progesterone receptor, breast cancer, steroid derivatives, estrogens, molecular docking