Data from The <i>a</i>3 Isoform Vacuolar Type H<sup>+</sup>-ATPase Promotes Distant Metastasis in the Mouse B16 Melanoma Cells

Abstract

<div>Abstract<p>Accumulating evidence indicates that the acidic microenvironments critically influence malignant behaviors of cancer including invasiveness, metastasis, and chemoresistance. Because the vacuolar-type H<sup>+</sup>-ATPase (V-ATPase) has been shown to cause extracellular acidification by pumping protons, we studied the role of V-ATPase in distant metastasis. Real-time PCR analysis revealed that the high-metastatic B16-F10 melanoma cells strongly expressed the <i>a</i>3 isoform V-ATPase compared to the low-metastatic B16 parental cells. Consistent with this, B16-F10 cells created acidic environments in lung metastases by acridine orange staining and strong <i>a</i>3 V-ATPase expression in bone metastases by immunohistochemistry. Immunocytochemical analysis showed B16-F10 cells expressed <i>a</i>3 V-ATPase not only in cytoplasm but also plasma membrane, whereas B16 parental cells exhibited its expression only in cytoplasm. Of note, knockdown of <i>a</i>3 V-ATPase suppressed invasiveness and migration with reduced MMP-2 and MMP-9 expression in B16-F10 cells and significantly decreased lung and bone metastases, despite that tumor growth was not altered. Importantly, administration of a specific V-ATPase <i>a</i>3 inhibitor FR167356 reduced bone metastasis of B16-F10 cells. These results suggest that <i>a</i>3 V-ATPase promotes distant metastasis of B16-F10 cells by creating acidic environments via proton secretion. Our results also suggest that inhibition of the development of cancer-associated acidic environments by suppressing <i>a</i>3 V-ATPase could be a novel therapeutic approach for the treatment of cancer metastasis. <i>Mol Cancer Res; 9(7); 845–55. ©2011 AACR</i>.</p></div>