Targeting steroid receptors and aldo-keto reductases of 1C subfamily with bile acid derivatives: in vitro and in silico insights.

A library of 24 structurally diverse bile-acid derivatives, comprising 11 new derivatives and 13 previously reported analogues, was prepared. Twenty selected compounds were evaluated against six cancer cell lines and MRC-5 fibroblasts. Lactams 14, 15 and 17 and oxime 10 produced the strongest cell-line-dependent antiproliferative activities, with IC₅₀ values below 10 µM in selected cancer-cell models and MRC-5 IC₅₀ values above 100 µM. Interactions with the ligand-binding domains (LBDs) of estrogen receptor α (ERα), estrogen receptor β (ERβ), androgen receptor (AR) and glucocorticoid receptor (GR) were evaluated using yeast-based fluorescent biosensors. Compound 27 showed the highest affinity for ERβ-LBD, whereas compound 24 exhibited weak affinity for ERα-LBD. No detectable binding to AR-LBD was observed for the tested derivatives, while compounds 10 and 30 showed the highest affinity for GR-LBD. Preliminary screening identified several potent AKR1C3 and AKR1C4 inhibitors, while concentration-dependent assays confirmed the inhibitory activity of compounds 23 and 30 against AKR1C3, with IC₅₀ values of 23.22 and 24.61 μM, respectively. Molecular docking generated plausible binding models for selected compounds within the AKR1C3 and GR ligand-binding sites. Matched-series analysis did not reveal a universally favourable chemotype or a simple relationship between cLogP, TPSA and biological activity. Instead, activity depended on the position of modification and the underlying bile-acid scaffold. These findings highlight the bile-acid framework as a versatile and tunable scaffold for anticancer drug discovery, in which variation of functional group identity and position can generate distinct biological profiles and provide different starting points for further optimization.