The vacuolar-ATPase modulates matrix metalloproteinase isoforms in human pancreatic cancer

Abstract

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 V1E 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.

The Function of Vacuolar ATPase (V-ATPase) a Subunit Isoforms in Invasiveness of MCF10a and MCF10CA1a Human Breast Cancer Cells

“…Neutralization of the acidic extracellular pH of tumors has been shown to prevent the formation of metastases in mouse models (38). Moreover, pharmacologic or genetic disruption of V-ATPase activity has been shown to reduce matrix metalloproteinase activity in pancreatic cancer cells (27). The data presented in this study are consistent with this hypothesis but do not rule out other possible roles for V-ATPases in invasion.…”

“…The role of different populations of V-ATPases containing particular isoforms of subunit a has begun to be probed in a number of cancers types, including breast cancer, melanoma, and pancreatic cancer. In the cases of melanoma and pancreatic cancer cells, high expression of the a3 isoform was found to be critical for invasion of highly metastatic cancer cells (27,28). In the case of breast cancer cells, comparison of two unrelated cell lines (MCF-7 and MDA-MB231) showed that the more invasive MDA-MB231 cells express much higher levels of both a3 and a4 compared with the less invasive MCF-7 cell line (24).…”

“…In human pancreatic ductal adenocarcinoma, high V-ATPase expression correlates with increasing cancer grade, and V-ATPases localize to the plasma membrane of the invasive Panc-1 pancreatic cancer cell line (27). Furthermore, blocking V-ATPase activity inhibits pancreatic cancer cell invasion and reduces matrix metalloproteinase 9 activity (27).…”

Vacuolar ATPase as a potential therapeutic target and mediator of treatment resistance in cancer

“…Other studies have described expression of V‐ATPase/specific subunits in pancreatic cancer,32, 33 nonsmall cell lung cancer,34 oral squamous cell carcinoma,35, 36 ovarian cancer,37 cervical cancer,38 breast cancer,39, 40 gliomas,41 and hepatocellular carcinoma 42. A summary of studies investigating clinical significance of V‐ATPase in cancer is provided in Table 1.…”

“…Increased cancer cell invasive activity is frequently associated with aberrant V‐ATPase plasma membrane localization suggesting that increased acidification of the extracellular space plays an important role 29, 33, 34, 37, 47, 48, 49, 50, 51, 52…”