Vasopressin boosts the antiproliferative effect of dynasore and wortmannin in triple-negative breast cancer cells.

Arginine vasopressin hormone (AVP) is ectopically expressed in breast cancer. Also, in intestinal epithelial and mesangial cells, for example, it acts as a growth-promoting factor when it binds to the GPCR receptor and triggers multiple downstream mitogenic signalling pathways leading to cell proliferation. As Dynamin 2 GTPase (Dyn2) is an integral protein involved in membrane receptor endocytosis, it is unclear how far AVP and Dynasore (DYN), a selective Dyn2 GTPase inhibitor, can modulate the proliferation of invasive breast cancer cells. To explore this, triple-negative breast cancer cells (MDA MB-231), which express V1A, were exposed to 100 nM AVP for 24 h, either alone or in combination with DYN. The cytotoxic effect, apoptosis, and autophagy-mediated cell death were assessed and compared to untreated cells and cells in which the PI3K/AKT pathway was inhibited by wortmannin (Wort). Also, cell cycle progression, migration, and the expression of the drug-resistance gene were investigated. We found that AVP alone developed apoptosis in about 20% of cells, and in the presence of DYN, apoptosis increased to 28%. This was associated with overexpression of Bax and Caspase-3, cell cycle arrest in G0/G1 phase, and regression of cell migration and invasion. In parallel, wortmannin alone or in combination with DYN induced apoptosis in 29% and 35% of cells, respectively. The autophagy markers (the microtubule-associated protein (LC3II) and Beclin1 mRNA) increased in AVP and AVP+DYN-treated cells but decreased in Wort and Wort+DYN-treated cells. Mechanistically, dual treatments (AVP+DYN or Wort+DYN) decreased the AKT activation and downregulated the multidrug resistance gene (MDR1). These findings suggest that AVP demonstrates apoptosis- and autophagy-related cell death and exerts a synergistic antiproliferative effect with DYN against invasive breast cancer cells.