Azelastine Inhibits Triple-Negative Breast Cancer Cell Viability via an ARF1-Dependent Mechanism

Triple-negative breast cancer (TNBC), lacking targetable receptors such as estrogen receptors, progesterone receptors, and human epidermal growth factor receptor 2, is an aggressive subtype with limited treatment options and highlights the need for novel therapeutic strategies. Here, we report that azelastine, a clinically approved H1-antihistamine, suppresses the viability of MDA-MB-231 TNBC cells in a dose- and time-dependent manner with 40% inhibition at 30 µM and 65% at 50 µM after 72 hours. Although histamine receptor 1 (HRH1) is functionally expressed in these cells, neither histamine stimulation nor HRH1 knockdown influenced cell survival, suggesting an HRH1-independent mechanism. Analysis of patient datasets revealed that ADP-ribosylation factor 1 (ARF1) is overexpressed in TNBC and associated with poor survival. Notably, inhibition of ARF1 by golgicide A abolished the cytotoxic effect of azelastine via the cationic amphiphile pathway. These findings suggest that azelastine exerts its anticancer effects through ARF1, not HRH1, and highlight its potential for drug repositioning in ARF1-driven TNBC.