KAI Expression Prevents IL-8-Mediated Endothelial Gap Formation in Late-Stage Melanomas
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Oncogene (2014) 33, 2898–2908 & 2014 Macmillan Publishers Limited All rights reserved 0950-9232/14 www.nature.com/onc ORIGINAL ARTICLE CD82/KAI expression prevents IL-8-mediated endothelial gap formation in late-stage melanomas P Khanna1, C-Y Chung2, RI Neves2,3,4,5,6, GP Robertson2,3,4,7,8,9 and C Dong1,8 Melanoma cells facilitate endothelial gap formation, the first step during tumor transendothelial migration, which is mediated by both adhesion and endogenously produced chemokines (in particular, interleukin-8 (IL-8)). Tetraspanins are localized to the cell surface in cancer and participate in various functions including invasion of tissues mediated by secretion of cytokines and matrix metalloproteinases. However, little is known about the role of CD82 tetraspanins in malignant melanomas during cancer cell invasion. In this study, we investigated the functional importance of CD82 expression in melanoma-mediated gap formation by using cDNAs to induce CD82 expression in highly invasive melanoma cell lines. Results showed that CD82 expression inhibited melanoma cell-induced gap formation, melanoma cell extravasation in vitro and subsequent lung metastasis development in vivo. Mechanistic studies showed that inducible expression of CD82 in highly metastatic melanoma cells significantly increased p21 expression upon binding of Duffy antigen receptor group (DARC), inducing tumor cell senescence and interrupting IL-8-mediated vascular endothelial (VE)-cadherin disassembly. Taken together, these studies provide a rationale for using drug therapies that restore CD82 expression and inhibit IL-8 production to inhibit late-stage melanoma cell extravasation and subsequent metastasis development. Oncogene (2014) 33, 2898–2908; doi:10.1038/onc.2013.249; published online 22 July 2013 Keywords: melanoma metastasis; CD82; IL-8; adhesion INTRODUCTION Previous work has shown that CD82 binds to Duffy antigen Metastasis is a complex process requiring melanoma cell receptor/chemokine group (DARC), and furthermore, that DARC detachment from its primary location and migration through expression in endothelial cells is necessary for CD82-mediated 16,17 blood or circulatory systems to secondary sites. Once cancer cells tumor suppression. Binding of CD82 on tumor cells to DARC metastasize to reach distant organs, cancers become increasingly receptors on endothelial cells prevents invasion of CD82-positive difficult to treat using current therapies warranting the need tumor cells by inducing senescence in CD82 þ cells. DARC also to elucidate molecular mechanism during this process.1–3 One binds C–X–C and C–C cytokine receptors (including interleukin 16,18 important event during cancer metastasis is melanoma cell (IL)-8) secreted by highly metastatic melanoma cells. extravasation through the endothelial vessels, which requires4,5 IL-8 has been shown to be an important factor in mediating (i) the breakdown of vascular endothelial (VE)-cadherins to form tumor cell extravasation through endothelial cells and underlying 19,20 gaps, (ii) penetration of the endothelial barrier and (iii) migration extracellular matrix. IL-8 binds with high affinity to CXCR2 and 21,22 of tumor cells through blood vessels into tissues to form DARC rather than CXCR1. Studies in fibroblasts have shown metastatic lesions. These events are mediated by adhesion that knocking down DARC diminishes cell senescence and molecules, inflammatory cytokines and proteases that degrade increases tumor cell extravasation.18,23,24 In normal physiology, the underlying extracellular matrix.5–7 DARC on endothelial cells modulates IL-8 signaling by acting as a Tetraspanins are a family of membrane proteins present in all ‘chemokine sink’ where DARC binds to chemokines, but does not tissue types that have a vital role in a wide spectrum of biological activate downstream signaling pathways.25 During tumor-induced functions.8,9 In cancers, tetraspanins (including CD82) have a vital inflammation, excess secretion of IL-8 within the tumor role in cellular invasion, particularly during cell movement.10–12 microenvironment disrupts this homeostasis. In melanoma cells, Studies have found that expression levels of CD82 tetraspanins these effects are exacerbated by synergistic secretion of IL-8 from decrease in highly metastatic cancers, increasing tumor endothelial cells bound to melanoma cells, facilitating migration cell extravasation.13,14 While the metastatic-suppressive effects of melanoma cells through the blood vessels.26–31 Upon IL-8 of CD82 have been demonstrated in cell, animal and patient binding to CXCR2 receptors, signaling pathways such as models,12,13,15 the complex molecular mechanism by which CD82 phosphatidylinositol-3 kinase and/or p38 mitogen-activated expression suppresses tumor cell extravasation remains unclear. protein kinase are activated. This signaling cascade inhibits 1Department of Bioengineering, The Pennsylvania State University, University Park, PA, USA; 2Department of Pharmacology, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 3Department of Dermatology, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 4Penn State Melanoma Therapeutic Program, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 5Cutaneous Oncology Program, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 6Department of Surgery, Division of Plastic Surgery, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 7Department of Pathology, The Pennsylvania State University College of Medicine, Hershey, PA, USA; 8Pennsylvania State Melanoma Center, The Pennsylvania State University College of Medicine, Hershey, PA, USA and 9The Foreman Foundation for Melanoma Research, The Pennsylvania State University College of Medicine, Hershey, PA, USA. Correspondence: Professor C Dong, Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA or Professor GP Robertson, Department of Pharmacology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. E-mail: [email protected] or [email protected] Received 22 November 2012; revised 23 March 2013; accepted 19 April 2013; published online 22 July 2013 Inhibition of IL-8-mediated endothelial gap formation by CD82/KAI P Khanna et al 2899 tumor cell senescence and trigger internalization of VE-cadherin western blot analysis (Figure 1e, right panels). As CD82 À cells junctions in the endothelial cells forming gaps on endothelial migrate under low shear stresses (0.625 dyn/cm2) rather than high monolayers.32–38 Although several studies have focused on shear stresses (2 dyn/cm2), these results show that CD82 mediates CD82 and DARC interactions, the role of CD82 in regulating IL-8 the motility and subsequent extravasation of tumor cells rather signaling remains unclear. than adhesion of tumor cells. However, the role of CD82 in tumor In melanoma cells, IL-8 binding to endothelial cells have an cell extravasation remains unknown. important role in regulating VE-cadherin disassembly via activa- CD82 expression in highly metastatic lines dramatically reduces tion of CXCR2 receptors.37 However, previous literature shows that in vitro gap formation. As VE-cadherin junctions serve as the ectopic expression of CXCR2 in tumor cells results in tumor cell primary mediators of endothelial permeability,37,41 we senescence.18 These studies show that during oncogene-induced hypothesized that CD82 regulates these endothelial junctions. senescence there is an increase in IL-8 that binds CXCR2 receptors Human umbilical vein endothelial cells (HUVECs) were grown to on tumor cells to reinforce tumor cell growth arrest 98–99% confluency on coverslips and cocultured with A375M and migration.18 In cancer cells, cell senescence can be reversed melanoma cells transfected with 3.1 vector or CD82 cDNAs. by knocking down CXCR2 expression.16,39 Although several Quantification of the total gap area shows a significant reduction studies have found that CD82 binding DARC induces tumor cell in the total gap area and gap sizes in cells transfected with CD82 senescence via a p21-dependent mechanism,40–47 the effects of (Figure 2a, left) compared with the control cases (3.1 vector), CD82 on IL-8 have not been elucidated. where total gap area and sizes of the gaps are much larger. In this work, we showed that ectopic CD82 expression These results lead to the conclusion that high levels of CD82 suppresses IL-8 secretion and that binding of CD82 tetraspanins expression prevented gap formation. Conversely, knocking down to DARC receptors interrupts IL-8 signaling in endothelial cells. The CD82 expression using small interfering RNA (siRNA) increases gap p21/Waf1 protein is a cyclin-dependent kinase inhibitor, which formation (Figure 2a, right). Gap formation is one important step binds active cyclin-dependent kinase 2 or cyclin-dependent kinase during tumor cell extravasation.37 We found that reintroducing 4 complexes.43,44 Inhibition of cyclin-dependent kinase complexes CD82 expression in highly invasive melanoma cells decreased prevents progression of cells through the G1 phase of the cell tumor cell extravasation through HUVEC monolayers after 4 h cycle, resulting in growth arrest of cells or cellular senescence. (Figure 2b, top and bottom left panels). CD82 expression in cells Consistent with previous work, melanoma cells expressing was analyzed using western blot analysis (Figure 2b, top and physiological levels of CD82 bound