Expression of Interleukin-8 Receptor CXCR2 and Suppressor of Cytokine Signaling-3 in Astrocytic Tumors

Penelope Korkolopoulou,Nikolaos Kavantzas,Paraskevi Fragkou,Elias A El-Habr,Vassilis Samaras,Efstratios Patsouris,Athanasios G Papavassiliou,Georgia Levidou,Efstathios Boviatsis,Athanasios Zisakis,Christina Piperi,Christos Adamopoulos

doi:10.2119/molmed.2011.00449

Abstract

The aim was to expand recently published information regarding the significance of the interleukin (IL)-8/p-STAT-3 (signal transducer and activator of transcription) pathway in astrocytomas, focusing on the IL-8 receptor, chemokine (C-X-C motif) receptor 2 (CXCR2), and the STAT-3 inhibitor SOCS-3 (suppressors of cytokine signaling). A total of 91 paraffin-embedded human astrocytoma tissues (grades II-IV) were investigated for the association of SOCS-3 and CXCR2 expression with clinicopathologic and morphometric microvascular characteristics, vascular endothelial growth factor (VEGF), IL-8 and p-STAT-3 expression and patient survival. Peripheral IL-8 secretion levels were assessed by enzyme-linked immunosorbent spot (ELISPOT). SOCS-3, p-STAT-3 and CXCR2 protein levels were also quantified by Western immunoblotting in six cases, and the protein levels of SOCS-3 and CXCR2 were correlated with the immunohistochemical expression of the respective proteins. All CXCR2-positive cases by Western immunoblotting displayed increased peripheral IL-8 secretion levels. Treatment of primary glioblastoma cell cultures with exogenous IL-8 enhanced proliferation, and this effect was inhibited by treatment with a neutralizing anti-CXCR2 antibody. SOCS-3 and CXCR2 were expressed by neoplastic astrocytes in 92.4% and 48.78% of cases, respectively, with their levels increasing with histological grade and extent of necrosis. VEGF expression and microvessel density, CXCR2 and IL-8 levels were interrelated. SOCS-3 and p-STAT-3 were co-expressed in 85.7% of cases, although they were not interrelated. In univariate survival analysis, increased SOCS-3 expression and the presence of CXCR2 adversely affected survival, whereas in multivariate analysis, only CXCR2 remained significant. The prognostic significance of CXCR2 was validated in an independent set of 63 patients. Our data implicate IL-8/CXCR2 signaling pathway in the progression and regulation of angiogenesis in astrocytomas and provide a rationale for CXCR2 therapeutic exploitation in these tumors.

Highlights

Glioblastoma, the most common neoplasm among diffuse infiltrating astrocytomas, is notorious for its ability to evade immunosurveillance as well as for its invasive and angiogenic properties [1]
Western Blot Analysis The CXCR2 and suppressors of cytokine signaling (SOCS)-3 expression levels by Western blot in the examined six cases were found to correlate with the immunohistochemical expression of the respective proteins in the same cases (Figures 1A, B)
The number of IL-8–secreting cells was markedly increased in patients with astrocytomas compared with healthy controls as previously described [15]

Summary

Introduction

Glioblastoma, the most common neoplasm among diffuse infiltrating astrocytomas, is notorious for its ability to evade immunosurveillance as well as for its invasive and angiogenic properties [1]. Direct and indirect evidence links the chemoattractant and proinflammatory CXC chemokine interleukin (IL)-8 to the invasive potential and rapid growth of glioblastoma cells. IL-8, like all ELR + CXC chemokines, is known to harbor potent angiogenic properties related to the Glu-Leu-Arg (ELR) motif immediately preceding its first Nterminal cysteine residue [2]. The biologic effects of IL-8 are mediated by two highly related G protein–coupled receptors: chemokine (C-X-C motif) receptor 1 (CXCR1; IL-8 R1) and CXCR2 (IL-8 R2). IL-8/CXCR1 autocrine signaling is presumably partly responsible for the glioblastoma-invasive phenotype, since downregulation of IL-8 or CXCR1 or si-

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Conclusion