10β-Hydroxyestra-1,4-diene-3,17-dione as potential antiproliferative agent: in vitro biological evaluation and in silico studies

Abstract

10β-Hydroxyestra-1,4-diene-3,17-dione (HEDD) is a natural product described as having interesting biological activities. However, the antiproliferative properties of this quinol are barely studied. Then, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed in six cell lines (MCF-7, T47-D, LNCaP, HepaRG, Caco-2 and NHDF).Additionally, an in vitro estrogenicity assay and a cell viability analysis together with in silico molecular docking studies were carried out in order to understand the potential mechanism of cytotoxicity. Computational predictions of its pharmacokinetic and toxicity properties were also performed. HEDD displayed cytotoxic activity, particularly against hormone-dependent cancer cells and the flow cytometry analysis revealed that HEDD markedly reduced the viability of hepatic cancer cells. The molecular docking studies suggested a strong affinity towards the estrogen receptor α and 17β-hydroxysteroid dehydrogenase type 1. Moreover, it was predicted that HEDD may have good oral bioavailability and a low maximum tolerated dose in humans.

10β-Hydroxyestra-1,4-diene-3,17-dione Does Not Bind to the Nuclear Estrogen Receptor α

“…Additionally, the authors’ docking of HEDD to aromatase should also be considered highly irrelevant in a biochemical context, because Canário et al (2022) should have been aware that conversion of a para -quinol to the corresponding estrogen is a reductive process, while aromatase produces estrogens from androgens by a three-step oxidative process (Yoshimoto and Guengerich, 2014; Prokai et al, 2013; Prokai-Tatrai et al, 2018).…”

“…Contradicting and disregarding these published experimental data yet adopting our HEDD acronym, Canário et al (2022) has recently asserted via their in silico docking study a strong binding of HEDD to ERα (–10.1 kcal/mol), which would essentially indicate binding as strong as that of ERα’s natural co-crystallized ligand E2, the main human estrogen, with a binding free energy of −9.9 kcal/mol. This would imply that ERα was highly tolerant to the replacement of the phenolic A-ring of E2 with a non-aromatic para -quinol in HEDD, disputing the published crystal structure of ERα-E2 complex (Tannenbaum et al, 1998) and extensive pharmacophore studies in this regard.…”

“…Nevertheless, our attempts to reproduce HEDD’s docking to ERα using the Autodock Vina protocol and parameters provided by Canário et al (2022) failed to generate a docked pose with the purported binding energy of the bound complex. A close examination of their virtual binding pocket also revealed that at least one residue was labelled unknown (“UNK1”) near the critical ligand-binding site of their reported HEDD–ERα complex, which indicated an unspecified alteration of the published receptor’s structure.…”

“…In support of the latter, the absence of estrogen-derived para -quinols’ in vivo uterotrophic effects has also been well documented. Via in silico docking, a recent publication by Canário et al (2022) reported a robust binding of HEDD (Figure 1B) to ERα. The authors claimed a strong binding of HEDD — as strong as that of its natural ligand, 17β-estradiol (E2), the main human estrogen.…”

“…However, an examination of the virtual binding pocket revealed that at least one residue near the critical ligand-binding site of their reported HEDD–ERα complex was labelled as “unknown” indicating thereby alteration of the receptor’s published structure (Tannenbaum et al, 1998; Bafna et al, 2020) to fit the ligand. Based on these arguments, the contradictory result by Canário et al (2022) on HEDD’s binding to ERα should be dismissed.…”