Ergotamine-Loaded Nanoparticles for Targeting Microtubule Dynamics in Triple-Negative Breast Cancer Cells

Microtubule-targeting agents (MTAs) are known to disrupt α–β-tubulin dimers, but their therapeutic effectiveness is impeded in drug-resistant cancer. Herein, we reported in silico and in vitro screening of FDA-approved drugs to identify a repurposed drug capable of targeting α–β-tubulin dimers in triple-negative breast cancer (TNBC). Molecular docking and molecular dynamics simulations, followed by experimental validation in triple-negative MDA-MB-231 and MDA-MB-468 cell lines, identified ergotamine as a potential MTA. Cytotoxicity studies revealed a concentration-dependent reduction in cell survival, with half-maximal inhibitory concentration (IC50) values of approximately 37 μM for MDA-MB-231 and 29 μM for MDA-MB-468 cells. Furthermore, in three-dimensional (3D) tumor spheroid models, ergotamine significantly reduced cell viability, indicating its potential efficacy in targeting solid tumor architecture. It exhibited a microtubule-depolymerizing effect, as evidenced by decreased tubulin expression in Western blot analysis and immunofluorescence assays. Treatment resulted in a significant decrease of both α-tubulin and β-tubulin expression, with reductions of 1.26- and 1.75-fold in MDA-MB-231 cells and 2.94- and 1.85-fold in MDA-MB-468 cells, respectively. Further, ergotamine treatment depolarized the mitochondrial membrane potential, promoting early apoptosis, with elevated reactive oxygen species (ROS) levels and altered tubulin dynamics. Finally, ergotamine-loaded gold nanocluster-embedded transferrin–PEG nanoparticles (LTPNC) were developed, which exhibited pronounced anticell proliferative effects by targeting TNBC cells. This study highlights ergotamine as a potential microtubule-targeting agent with significant anticancer effects against TNBC, along with the concomitant development of a nanoparticle-based drug delivery system.