Synthesis and in vitro evaluation of tetrahydroquinoline derivatives as antiproliferative compounds of breast cancer via targeting the GPER

Background: Some reports have demonstrated the role of the G Protein-coupled Estrogen Receptor (GPER) in growth and proliferation of breast cancer cells. Objective: In an effort to develop new therapeutic strategies against breast cancer, we employed an in silico study to explore the binding modes of tetrahydroquinoline 2 and 4 to be compared with the reported ligands G1 and G1PABA. Methods: This study aimed to design and filter ligands by in silico studies determining their Lipinski's rule, toxicity and binding properties with GPER to achieve experimental assays as anti-proliferative compounds of breast cancer cell lines. Results: In silico studies suggest as promissory two tetrahydroquinoline 2 and 4 which contain a carboxyl group instead of the acetyl group (as is needed for G1 synthesis), which add low (2) and high hindrance (4) chemical moieties to explore the polar, hydrophobic and hindrance effects. Docking and molecular dynamics simulations of the target compounds were performed with GPER to explore their binding mode and free energy values. In addition, the target small molecules were synthesized and assayed in vitro using breast cancer cells (MCF-7 and MDA-MB-231). Experimental assays showed that compound 2 decreased cell proliferation, showing IC₅₀ values of 50μM and 25μM after 72h of treatment of MCF-7 and MDA-MB-231 cell lines, respectively. Importantly, compound 2 showed a similar inhibitory effect on proliferation as G1 compound in MDA-MB-231 cells, suggesting that both ligands reach the GPER-binding site in a similar way, as was demonstrated through in silico studies. Conclusion: A concentration-dependent inhibition of cell proliferation occurred with compound 2 in the two cell lines regardless of GPER.