Abstract 326: Prognostic value of KIF14 and MDM4 in Ewing's sarcoma

Rearrangements of the long arm of chromosome 1 are widely recognized in many cancers including Ewing9s sarcoma (EWS). Copy number alterations through genomic gains and aneuploidy of chromosome 1 suggest the presence of loci responsible for EWS progression. We report here our investigation of mapping the region 1q32, which spans 4.2Mb and encompasses two candidate oncogenes that may contribute to EWS pathogenesis: KIF14 and MDM4. The genes encode proteins involved in the final phase of cytokinesis, in cell survival, and replicate early in the cell cycle. These findings suggest the presence of important proliferation-regulating genes on chromosome 1q implicated in driving progression of EWS. We hypothesize that secondary alterations of KIF14 and MDM4, their replication pattern, along with chromosome 1 aneuploidy, are associated with clinical parameters of progression. Multi - color interphase fluorescence in situ hybridization (FISH) was performed on a tissue microarray (TMA) including 112 patient specimens using in house BAC probes for KIF14 and MDM4. Gain was defined by the presence of more than three hybridization signals per interphase nucleus with simultaneous intact centrosome signal occurring in more than 5% of nuclei. Aneuploidy was considered when the tumor cells exceeded the mean control +2 SD stage. We classified gene replication pattern as synchronous (SS, DD), or asynchronous (SD), according to the replication status of two homologous loci. Multiplet signals were analyzed when we observed clusters of more than 3 signals separated by less than one signal diameter. Statistical analyses were performed using SPSS program. A p-value of less than 0.05 was considered significant. Copy numbers alterations were detected in 27/112 (24.1%) EWS patients. FISH analyses indicated 1q32 locus gain in 2/27 (7.4%), polysomy in 19/27 (70.4%) and 1q32 locus gain plus polysomy in 6/27 (22.2%). Disease-free survival analysis of the 1q32 gain plus aneuploidy of chromosome 1 versus only gain at 1q32 identified a shorter time interval in those patients that presented with 1q32 gain plus aneuploidy of chromosome 1 concurrently (p=0.04). Interestingly, univariate data analysis showed association with asynchronous gene replication pattern of KIF14 and polysomy (p=0.040) as well as tumor relapse (p=0.031). Furthermore, the multiplet replication pattern of MDM4 showed association with polysomy (p=0.014) and with poor clinical treatment response (p=0.045). It was noteworthy that in this cohort no statistically significant association was seen between treated and untreated groups. Genomic secondary alterations of 1q32 and simultaneous extra copies of chromosome 1 appear to define a small clinical subset of EWS patients with distinctly poor outcome. Significantly, the asynchronous gene replication pattern of KIF14 and MDM4 has potential prognostic value in stratifying of patients for risk, in which their corresponding products are possible therapeutic targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 326.