Structural analysis and biological activities of BXL0124, a gemini analog of vitamin D

Vitamin D Analogs Bearing C-20 Modifications Stabilize the Agonistic Conformation of Non-Responsive Vitamin D Receptor Variants

The Vitamin D receptor (VDR) plays a key role in calcium homeostasis, as well as in cell proliferation and differentiation. Among the large number of VDR ligands that have been developed, we have previously shown that BXL-62 and Gemini-72, two C-20-modified vitamin D analogs are highly potent VDR agonists. In this study, we show that both VDR ligands restore the transcriptional activities of VDR variants unresponsive to the natural ligand and identified in patients with rickets. The elucidated mechanisms of action underlying the activities of these C-20-modified analogs emphasize the mutual adaptation of the ligand and the VDR ligand-binding pocket.

Development of novel Gemini-cholesterol analogues for Retinoid-related Orphan Receptor

Retinoic-acid-related Orphan Receptors (RORs) regulate maintenance of the circadian rhythm and immune response among others and are involved in increasing number of pathologies including autoimmune diseases, cancer and neurological disorders...

Analysis of the Transcriptome: Regulation of Cancer Stemness in Breast Ductal Carcinoma In Situ by Vitamin D Compounds

Ductal carcinoma in situ (DCIS), which accounts for one out of every five new breast cancer diagnoses, will progress to potentially lethal invasive ductal carcinoma (IDC) in about 50% of cases. Vitamin D compounds have been shown to inhibit progression to IDC in the MCF10DCIS model. This inhibition appears to involve a reduction in the cancer stem cell-like population in MCF10DCIS tumors. To identify genes that are involved in the vitamin D effects, a global transcriptomic analysis was undertaken of MCF10DCIS cells grown in mammosphere cultures, in which cancer stem-like cells grow preferentially and produce colonies by self-renewal and maturation, in the presence and absence of 1α25(OH)₂D₃ and a vitamin D analog, BXL0124. Using next-generation RNA-sequencing, we found that vitamin D compounds downregulated genes involved in maintenance of breast cancer stem-like cells (e.g., GDF15), epithelial-mesenchymal transition, invasion, and metastasis (e.g., LCN2 and S100A4), and chemoresistance (e.g., NGFR, PPP1R1B, and AGR2), while upregulating genes associated with a basal-like phenotype (e.g., KRT6A and KRT5) and negative regulators of breast tumorigenesis (e.g., EMP1). Gene methylation status was analyzed to determine whether the changes in expression induced by vitamin D compounds occurred via this mechanism. Ingenuity pathway analysis was performed to identify upstream regulators and downstream signaling pathway genes differentially regulated by vitamin D, including TP63 and vitamin D receptor -mediated canonical pathways in particular. This study provides a global profiling of changes in the gene signature of DCIS regulated by vitamin D compounds and possible targets for chemoprevention of DCIS progression to IDC in patients.

Vitamin D and Its Synthetic Analogs

For many individuals, in particular during winter, supplementation with the secosteroid vitamin D₃ is essential for the prevention of bone disorders, muscle weakness, autoimmune diseases, and possibly also different types of cancer. Vitamin D₃ acts via its metabolite 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] as potent agonist of the transcription factor vitamin D receptor (VDR). Thus, vitamin D directly affects chromatin structure and gene regulation at thousands of genomic loci, i.e., the epigenome and transcriptome of its target tissues. Modifications of 1,25(OH)₂D₃ at its side-chain, A-ring, triene system, or C-ring, alone and in combination, as well as nonsteroidal mimics provided numerous potent VDR agonists and some antagonists. The nearly 150 crystal structures of VDR’s ligand-binding domain with various vitamin D compounds allow a detailed molecular understanding of their action. This review discusses the most important vitamin D analogs presented during the past 10 years and molecular insight derived from new structural information on the VDR protein.