Design, synthesis and biological evaluation of small molecules for controlling cellular development

Abstract

Cellular differentiation is a process directed by a wide range of controlling signaling molecules and pathways. All-trans-retinoic acid (ATRA) is one such compound that shows a wide range of biological activity. The endogenous effects of ATRA have the potential to be translated into many in vitro and in vivo applications; however, its administration is associated with many drawbacks. Consequently, a large group of synthetic analogues known as synthetic retinoids - that are structurally similar to ATRA have been prepared and tested in vitro in the search for higher stability and more potency. A small library of stable synthetic retinoids known as EC and GZ derivatives were prepared and their biological activity investigated using TERA2.cl.SP12 human embryonal carcinoma (EC) stem cells and SHSY5Y neuroblastoma cells. Two compounds, EC23 and GZ25 were found to inhibit cellular proliferation and induce neural differentiation in both cell lines. EC50s showed higher binding affinity of these two analogues to all RAR types and was confirmed by how they fit into the binding pocket of the different RARs. They bind into the binding pocket through a hydrophilic network of carboxylate group with Arg (salt bridge) and Ser (two hydrogen bonds) residues similar to ATRA. These effects were thoroughly characterized and quantified by monitoring the phenotypic changes of both cell lines and the gene expression markers such as RAR-β, PAX6, NeuroD1 which showed higher order of efficacy for induction of neuronal differentiation.In this study, the combined use of calculated chemical structures, molecular docking tools with receptor binding assays and biological characterization was useful to probe, and hence, understand the biological activity of certain synthetic retinoids with the ultimate goal of designing more specific synthetic retinoic acid derivatives.