Triclosan-Isatin Hybrids as Potent Anti-proliferative Agents Inducing S-Phase Arrest via DNA Gyrase Inhibition in Triple-Negative Breast Cancer

Abstract

A series of 1H-1,2,3-triazole-tethered TCS–isatin hybrid compounds were synthesized and evaluated for their antiproliferative activity against triple-negative breast cancer (TNBC). These hybrids exhibited remarkable potency against MDA-MB-231 and MDA-MB-468 cell lines, with three triclosan-dibromoisatin analogues having ethyl, propyl, and butyl linkers (10m, 10n, and 10o, respectively) demonstrating particularly strong efficacy. The most potent hybrid having propyl linker (10n) outperformed standard chemotherapeutics, showing 8-, 3-, and 14-fold greater activity against MDA-MB-231 and 9-, 5-, and 13-fold greater activity against MDA-MB-468 compared to 5-fluorouracil (5-FU), cisplatin, and tamoxifen, respectively. The compounds exhibited low IC50 values (1.59–8.84 µM for MDA-MB-231; 1.14–7.56 µM for MDA-MB-468) alongside favorable selectivity indices, indicating potent anti-proliferative effects with minimal toxicity toward normal human HaCaT keratinocytes. Flow cytometric analysis revealed that compound 10n induced a dose-dependent S-phase arrest in MDA-MB-468 cells, confirming interference with DNA replication. To probe the mechanism of action, the most potent compounds 10n and 10o were assessed for E. coli DNA gyrase B inhibition. Both exhibited significant suppression of DNA supercoiling, confirming strong binding affinity to the enzyme and suggesting a potential role in topoisomerase-mediated anticancer activity.