Synthesis and Biological Evaluations of Ring Substituted Tetrahydroisoquinolines (THIQs) as Anti-Breast Cancer Agents

Breast cancer is a leading cause of mortality among women, resulting in more than half a million deaths worldwide every year. Although chemotherapeutic drugs remain the main stay of cancer treatment, it is observed that toxicity to normal cells poses a limitation to their therapeutic values. Moreover, the patient recovery rate from advanced breast cancer by chemotherapy is still unacceptably low. Tetrahydroisoqinoline derivatives (THIQs) were reported to act as selective subtype estrogen receptor antagonists/agonists and may serve as potential therapeutic agents for breast cancer. In continuation of previous work we systematically synthesized and characterized the tetrahydroisoquinoline (THIQs) analogs. In-vitro antiproliferative activity of new substituted tetrahydroisoquinoline analogs were evaluated against human ER (+) MCF-7 (breast), ER (−) MDA-MB-231 (breast) and Ishikawa (endometrial) cancer cell lines using the CellTiter-Glo luminescent cell viability assay. The most active compounds obtained in this study were 2b, 2i, and 3 g as demonstrated by their activity (IC(50)=0.2 μg/mL, 0.08 μg/mL; 0.61 μg/mL, 0.09 μg/mL; 0.25 μg/mL, 0.11 μg/mL) against MCF-7 and Ishikawa cell lines respectively, in comparison to Tamoxifen activity (IC(50)=3.99 μg/mL, 7.87 μg/ml). The newly synthesized molecules were docked in the active sites of the ER-α (PDB: 3ERT), ER-β (PDB: 1QKN) and alpha-beta tubulin taxol complex (1JFF) crystal structures to determine the probable binding modes (bioactive conformations) of the active compounds.