Identification of Vitamin D3-Based Hedgehog Pathway Inhibitors That Incorporate an Aromatic A-Ring Isostere

Abstract

Previous structure−activity relationship studies for vitamin D3 (VD3) inhibition of Hedgehog (Hh) signaling directed the design, synthesis, and evaluation of a series of VD3-based analogues that contain an aromatic A-ring mimic. Characterization of these compounds in a series of cellular assays demonstrated their ability to potently and selectively downregulate Hh pathway signaling. The most active of these, 17, inhibited pathway signaling in Hh-dependent mouse fibroblasts (IC 50 = 0.74 ± 0.1 μM) and cultured cancer cells (IC 50 values 3.8 ± 0.1 to 5.2 ± 0.2 μM). In addition, 17 demonstrated reduced activation of the vitamin D receptor (VDR) compared to VD3 in these cellular models. These results suggest that VD3-based analogues with an aromatic A-ring are a valid scaffold for the development of more selective and potent Hh pathway inhibitors and identify 17 as an intriguing lead from this class of compounds for further development. In addition, our analysis of Hh pathway inhibitors in cancer cells suggests that the murine basal cell carcinoma cell line ASZ001 and the human medulloblastoma cell line DAOY are appropriate in vitro cancer models for early stage evaluation of pathway inhibition.

Synthesis and Evaluation of Aminothiazole Derivatives as Hedgehog Pathway Inhibitors

“…Compound 18 exhibited no obvious toxicity up to 100 μ m against astrocytes and gastric epithelial cells GES‐1 ( Figure A ). DAOY cell lines were a suitable human MB model with constitutive Hh activation, which was reported to be resistant to vismodegib in vitro . As illustrated in Figure B , compound 18 decreased proliferation and survival of DAOY cells, although vismodegib was less active.…”

Structure–Activity Relationship Studies of Vitamin D3 Analogues Containing an Ether or Thioether Linker as Hedgehog Pathway Inhibitors

“…General protocols for cell culture, qPCR, and Hh inhibition in C3H10T1/2 and ASZ001 cells are as previously described . Data were analyzed with GraphPad Prism 5 and reported values represent the mean±SEM for at least two separate experiments carried out in triplicate.…”

“…[10] Since then, severals eries of VD3 analogues based on this hexahydroindane scaffold were synthesized and evaluated for their Hh inhibitory activity.T he majority of these compounds incorporate an aromaticA -ring mimic linked to the northern region throughavariety of tethers, including esters, amines, or amides. [11][12][13] Severalcompounds with improved anti-Hhactivity have been identified through these studies (Figure 1, 3-6). Our SAR for these analogues clearly demonstrated that ap henyl ring incorporating ah ydrophilic moiety at the meta-o rparaposition is necessary for potent Hh inhibition.…”

“…Since then, several series of VD3 analogues based on this hexahydroindane scaffold were synthesized and evaluated for their Hh inhibitory activity. The majority of these compounds incorporate an aromatic A‐ring mimic linked to the northern region through a variety of tethers, including esters, amines, or amides . Several compounds with improved anti‐Hh activity have been identified through these studies (Figure , 3 – 6 ).…”

Strategies to target the Hedgehog signaling pathway for cancer therapy

“…Based on these findings, Hadden and co‐workers conducted structural optimizations and further studied their mechanism of action. Among many synthesized analogs, Grundmann's alcohol ( 24 ) (IC 50 = 3.1 μM) was found to be effective against Hh‐dependent C3H10T1/2 cell lines, and showed comparable activity to VD3 (IC 50 = 4.1 μM) against the Hh pathway . Attempts to link an aromatic ring to the structure of compound 24 led to the discovery of representative compounds 25 , 26 , and 27 as potent and selective VD3‐like Hh inhibitors .…”