New Fluorescent Synthetic Retinoids as Potential RAR Agonists with Anticancer, Molecular Docking and ADME Assessments

Natural and synthetic retinoids are derivatives of vitamin A that mediate different transcriptional activities. Synthesis of fluorescent probes can be a useful tool in cellular imaging and understanding different regulatory signaling pathways. In this study, new fluorescent synthetic retinoid analogues (3a, 3b, 4a, and 4b) were prepared and biologically screened against six different cancer and normal cell lines for assessment of their anticancer and fluorescent activities. A combination of biological assays, such as MTT, flow cytometry, gene and protein expression analysis, DNA fragmentation, and ATPase activity assays, as well as in-silico and ADME studies, was performed. All new compounds showed anti-proliferative activity (2.09-132.70 µM) against different cancer cell types with minimal cytotoxicity (SI > 1), and the Caco-2 cancer cell line was selected for further in vitro investigation. All compounds showed cell cycle arrest at the SubG₀-G₁ phase with induction of early apoptosis and necrosis. Compound 4b showed a significant apoptotic effect by overexpression of Caspase-3 and Cyt-c genes, followed by compound 3a. All compounds showed anti-inflammatory activity by significantly down-regulating the IL-10 pro-inflammatory marker, while compounds 3b, 4a, and 4b specifically down-regulated IL-6. Retinoic acid receptors (RARs) were suggested as molecular targets confirmed by their overexpression of both gene and protein levels with molecular docking and molecular dynamic simulation studies. All fluorescent compounds showed intracellular fluorescent emission spectra with intracellular lipophilic properties. The new fluorescent synthetic retinoids showed dual activities as anticancer agents with fluorescence properties and can be used as useful probes in a variety of cellular imaging investigations.