RESUMEN
OBJECTIVES: Immunotherapeutic interventions in cancer have been considerably successful and widely accepted for cancer treatment, but are costly and cannot be afforded by all patients. Because of the high cost, the pharmaceutical research groups across the world are sufficiently motivated to discover or design small molecule inhibitors to treat cancer through inhibition of the immune checkpoint proteins previously targeted with monoclonal antibodies. The presented study was designed with an aim to establish raloxifene, a selective estrogen receptor modulator (SERM) as a potential ligand of the immune checkpoint protein Programmed death ligand-1 (PD-L1). METHODS: In the presented study, the in-silico approach was used for identifying a lead molecule against PD-L1. The hits were screened using the similarity-search method, and drug-likeliness analysis, and the leads were identified through ligand-docking using Autodock. In-vitro cytotoxicity analysis was carried out using the standard sulphorhodamine B (SRB) assay and the wound healing analysis to show the inhibition of cellular migration was performed using the standard scratch assay. RESULTS: The in-silico study revealed that raloxifene showed a high drug likelihood and higher binding affinity with PD-L1 as compared to the positive control (BMS-1166; BMS is Bristol Myers Squibb). The binding of raloxifene was shown to occur in the same region as the FDA-approved monoclonal antibodies atezolizumab and durvalumab, indicating the potential of raloxifene for PD1/PD-L1 blockade. In the in-vitro studies, raloxifene showed a time-dependent reduction in IC50 values for the cell line HCT116 (colon cancer). The scratch assay also revealed that raloxifene significantly reduced the migratory potential of HCT-116 cells in-vitro. CONCLUSIONS: PD-L1 is a potential target of the SERM raloxifene in-silico. Overall, this study is one step further towards immune checkpoint blockade using small-molecule inhibitors.
RESUMEN
A library of 49 analogs of imidazo[1,2-a]pyridine with 2-halo, aryl, styryl and phenylethynyl-substitution at C-2 position and N-/O-/S-methyl linkage at C-3 position, have been synthesized and evaluated for their anti-proliferative activity against breast (MCF-7, MDA-MB-231), pancreatic (MiaPaca-2), lung (A549), prostate (PC-3) and colon (HCT-116) cancer cell lines and normal cells (HEK-293). Among the screened compounds, 5b exhibited best anticancer potential in all tested cancer cells with IC50 ranging from 3.5 to 61.1 µM and no toxicity in normal cells. Further, mechanistic study of 5b revealed concentration dependent increased generation of ROS, reduced mitochondrial membrane potential (MMP), surface and nuclear morphological alterations and inhibition of colony formation in HCT-116 cells. Western blot results had shown that the cell death in HCT-116 colon cancer cells was achieved through the induction of apoptosis via upregulation of the PTEN gene and downregulation of AKT pathway. Similarly, 5b treatment induced caspase-3 cleavage which is a hallmark of apoptosis. Molecular docking and binding energy (ΔG) studies of hit 5b with respect to three important cancer targets (EGFR, mTOR and PI3Kα) revealed strong binding of inhibitor with PI3Kα (docking score -6.932 and ΔG -56.297).
