Molecular Dynamics Studies on the Enzalutamide Resistance Mechanisms Induced by Androgen Receptor Mutations

The second-generation antiandrogen enzalutamide, targeting androgen receptor (AR), was approved to treat castration resistant prostate cancer (CRPC) in 2012. Its resistance was observed when it was in the clinical research stage. AR mutation is the main factor of enzalutamide resistance. AR F876L and F876L_T877A mutations were reported to switch enzalutamide from AR antagonist to agonist, but W741C cannot. There are various mutations in the ligand binding domain of AR LBD, such as L701H, W741L, H874Y, T877A, and M895T, if these mutations can lead to drug resistance problem or not is not known. In this work, molecular dynamics (MD) simulations and molecular mechanics Generalized Born (GB) surface area (MM-GBSA) calculations were employed to explore the interaction mechanisms between enzalutamide and wild-type (WT)/mutant ARs. The simulation results indicate that helix 12 (H12), which lies on the top of the AR LBD like a cover, plays a vital role for the function of enzalutamide. When C-ring of enzalutamide locates near to H12, the distance between enzalutamide and H12 is reduced, which prevents H12 from closing and distort the coactivator binding site, resulting in the inactivation of transcription. In this case, enzalutamide acts as an AR antagonist. However, when the C-ring of enzalutamide is near to helix H11 or the Loop 11–12, H12 tends to close to form a coactivator binding site to facilitate transcription, enzalutamide acts as an AR agonist. Moreover, per-residue free energy decomposition analysis indicates that M895 and I899 are key residues in the antagonist mechanism of enzalutamide. J. Cell. Biochem. 118: 2792–2801, 2017.