The vacuolar-ATPase (V-ATPase) modulates matrix metalloproteinase (MMP) isoforms in human pancreatic cancer

The vacuolar-ATPase (v-ATPase) is a proton transporter found on many intra-cellular organelles and the plasma membrane (PM). The v-ATPase on PMs of cancer cells may contribute to their invasive properties in vitro. Its relevance to human cancer tissues remains unclear. We investigated whether the expression and cellular localization of v-ATPase corresponded to the stage of human pancreatic cancer, and its effect on matrix metalloproteinase (MMP) activation in vitro. The intensity of v-ATPase staining increased significantly across the range of pancreatic histology from normal ducts to pancreatic intra-epithelial neoplasms (PanIN) and finally pancreatic ductal adenocarcinoma (PDAC). Low-grade PanIN lesions displayed polarized staining confined to the basal aspect of the cell in the majority (86%) of fields examined. High-grade PanIN lesions and PDAC demonstrated intense and diffuse v-ATPase localization. In pancreatic cancer cells, PM-associated v-ATPase co-localized with cortactin, a component of the leading edge that helps direct MMP release. Blockade of the v-ATPase with concanamycin or shRNA targeting the V(1)E subunit reduced MMP-9 activity; this effect was greatest in cells with prominent PM-associated v-ATPase. In cells with detectable MMP-2 activities, however, treatment with concanamycin markedly increased MMP-2’s most activated forms. V-ATPase blockade inhibited functional migration and invasion in those cells with predominantly MMP-9 activity. These results indicate that human PDAC specimens demonstrate loss of v-ATPase polarity and increased expression that correlates with increasing invasive potential. Thus, v-ATPase selectively modulates specific MMPs that may be linked to an invasive cancer phenotype.