Abstract 1437: The activity of plasma membrane V-ATPases is critical for the invasion of breast cancer cells

Abstract

Abstract The V-ATPases are a family of ATP-driven proton pumps that have been implicated in breast cancer cell invasion. V-ATPases are found both intracellularly and on the plasma membrane of specialized acid-secreted cells and invasive cancer cells. As available inhibitors of the V-ATPase are membrane-permeable, it has not yet been examined whether intracellular or plasma membrane pumps are critical for invasiveness. It has been proposed that V-ATPases promote invasiveness by localizing to the plasma membrane. To test this hypothesis, we utilized two approaches to specifically inhibit the V-ATPases at the plasma membrane. First, we stably transfected invasive MB231 breast cancer cells with a V5-tagged construct of the membrane-embedded subunit c. This allows for extracellular expression of the V5 epitope. We then found that addition of an anti-V5 antibody specifically inhibited plasma membrane V-ATPase activity as well as in vitro invasion and migration of MB231 cells. Second, we utilized a biotin-conjugated form of the specific V-ATPase inhibitor bafilomycin to inhibit plasma membrane pumps. When bound to streptavidin, this compound is membrane impermeable. Addition of streptavidin-bound biotin-bafilomycin also inhibited in vitro invasion and migration of MB231 cells. These studies suggest that V-ATPases at the plasma membrane play a critical role in breast cancer cell invasion. We hypothesize that plasma membrane V-ATPases participate in invasion by creating an acidic microenvironment that promotes the activity of pH-dependent proteases. Overall, these results have significant implications for targeting the pump to prevent breast cancer metastasis. Citation Format: Kristina Cotter, Joseph Capecci, Souad Sennoune, Markus Huss, Martin Maier, Raul Martinez-Zaguilan, Michael Forgac. The activity of plasma membrane V-ATPases is critical for the invasion of breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1437. doi:10.1158/1538-7445.AM2015-1437