Data from Characterization of Gene Amplification–Driven SKP2 Overexpression in Myxofibrosarcoma: Potential Implications in Tumor Progression and Therapeutics

Abstract

<div>Abstract<p><b>Purpose:</b> Myxofibrosarcoma remains obscure in molecular determinants of clinical aggressiveness, for which we elucidated implications of <i>SKP2</i> amplification.</p><p><b>Experimental Design:</b> Array comparative genomic hybridization was applied on samples and cell lines (NMFH-1 to OH931) to search causal genes of tumor progression. <i>SKP2</i> gene dosage was determined in 82 independent tumors for clinical correlates. Stable SKP2 knockdown was achieved in myxofibrosarcoma cells to assess its oncogenic attributes and candidate mediators in prometastatic function. Pharmacologic assays were evaluated <i>in vitro</i> and <i>in vivo</i> for the therapeutic relevance of bortezomib.</p><p><b>Results:</b> DNA gains frequently involved 5p in which three amplicons were differentially overrepresented in samples behaving unfavorably, encompassing mRNA-upregulated <i>TRIO</i>, <i>SKP2</i>, and <i>AMACR</i> genes. Detected in NMFH-1 cells and 38% of tumors, <i>SKP2</i> amplification was associated with SKP2 immunoexpression and adverse prognosticators and independently predictive of worse outcomes. Nevertheless, SKP2-expressing OH931 cells and 14% of such tumors lacked gene amplification. Knockdown of SKP2 suppressed proliferation, anchorage-independent growth, migration, and invasion of sarcoma cells and downregulated motility-promoting genes, including <i>ITGB2</i>, <i>ACTN1</i>, <i>IGF1</i>, and <i>ENAH</i>. <i>In vitro</i>, bortezomib downregulated SKP2 expression at the mRNA level with p27<sup>kip1</sup> accumulation, induced caspase activation, and decreased cell viability in myxofibrosarcoma cells but not in fibroblasts. <i>In vivo</i>, bortezomib inhibited growth of NMFH-1 xenografts, the cells of which displayed decreased SKP2 expression but increased p27<sup>kip1</sup> and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling (TUNEL).</p><p><b>Conclusions:</b> As a predominant mechanism driving protein overexpression, <i>SKP2</i> amplification confers tumor aggressiveness in myxofibrosarcoma. The sensitivity of myxofibrosarcoma cells to bortezomib with SKP2-repressing effect indicates the potentiality of ubiquitin-proteasome pathway as a therapeutic target. <i>Clin Cancer Res; 18(6); 1598–610. ©2012 AACR</i>.</p></div>