In silico and in vitro drug repurposing strategy for targeting dopamine receptor D2 in colorectal Cancer treatment
Abstract
Background Colorectal cancer (CRC) remains a major global health burden due to its high incidence, mortality, and therapy resistance. Drug repurposing offers a promising approach to identify new treatments using approved drugs with known safety profiles. This study evaluates the potential of targeting dopamine receptor D2 (DRD2) in CRC using domperidone and fluphenazine decanoate. Methods DRD2 expression and genetic alterations in CRC were analyzed using Human Protein Atlas and cBioPortal databases. Overexpression in HT-29 cells was confirmed by qPCR relative to normal HDF cells. Molecular docking and 45 ns molecular dynamics simulations assessed the binding and stability of domperidone and fluphenazine decanoate with DRD2. Cytotoxicity was evaluated via MTT assay in HT-29 and HDF cells. HT-29 cells treated at IC₅₀ concentrations were further analyzed by qPCR for apoptosis, survival, and migration-related gene expression. Results DRD2 was markedly overexpressed approximately 40-fold in HT-29 cells versus HDF, as confirmed by bioinformatics and qPCR. Molecular docking indicated strong binding of both compounds, while molecular dynamics simulations showed greater stability for fluphenazine decanoate, with lower RMSF and SASA. Domperidone exhibited higher cytotoxicity in HT-29 cells (IC₅₀ = 23.89 μg/mL) but also substantial toxicity in HDF (IC₅₀ = 21.08 μg/mL), whereas fluphenazine decanoate showed a markedly improved safety profile (IC₅₀ = 789.3 μg/mL in HDF). Gene expression analysis revealed distinct responses: fluphenazine decanoate upregulated BAX and BCL2 and downregulated CASP3, while domperidone induced modest BAX with minimal effect on BCL2. Both compounds moderately downregulated BIRC5, and fluphenazine decanoate additionally upregulated MMP9. Conclusion Despite higher cytotoxicity, domperidone's toxicity to normal cells limits its potential. Fluphenazine decanoate showed better stability, safety, and regulated gene responses, supporting its promise as a repurposed DRD2-targeted therapy in CRC.