Synthesis and evaluation of third generation vitamin D3 analogues as inhibitors of Hedgehog signaling.

Abstract The Hedgehog (Hh) pathway is a developmental pathway with therapeutic potential as a target for a variety of cancers. In recent years, several vitamin D-based compounds have been identified as potent inhibitors of Hh signaling. These analogues contain aromatic phenol A-ring mimics coupled to the CD-ring side chain of vitamin D3 through modified seco -B regions. To continue structure-activity relationship studies on this class of Hh pathway inhibitors, multiple series of vitamin D-based analogues that contain an amine-based seco -B tether and/or incorporate a hydroxyl moiety on C-25 were designed and synthesized. These compounds were evaluated in multiple cell lines for their anti-Hh activity, and we identify analogues 16 , 21 , 22 as potent vitamin D-based Hh inhibitors (IC 50 values of 110–340 nM). We also performed a series of mechanism of action studies in knockout cell lines to further explore whether these analogues inhibit the Hh pathway through a known Hh pathway component or the vitamin D receptor. While the specific cellular target that mediates these effects remains elusive, our studies suggest multiple cellular targets may mediate the anti-Hh activity of this scaffold. Graphical abstract Image 1 Highlights • A new series of vitamin D3 analogues with modifications to C-25 were designed and synthesized. • Analogues containing a C-25 hydroxyl are inhibitors of Hedgehog (Hh) signaling and activators of the vitamin D receptor. • Analogues 16, 21, and 22 demonstrated low nanomolar inhibition of pathway signaling in Hh-dependent basal cell carcinoma. • Activation of the vitamin D receptor correlates to enhance down-regulation of Gli1 expression. [ABSTRACT FROM AUTHOR]