Gliosarcoma is a rare glioblastoma variant characterized by a biphasic tissue pattern with alternating areas displaying glial (GFAP-positive) or mesenchymal (reticulin-positive) differentiation. Previous analyses showed identical genetic alterations in both glial and mesenchymal tumor areas, suggesting that gliosarcomas are genetically monoclonal, and mesenchymal differentiation was considered to reflect the elevated genomic instability of glioblastomas. In the present study, we compared genome-wide chromosomal imbalances using array CGH (105K) in glial and mesenchymal tumor areas of 13 gliosarcomas. Patterns of gain and loss were similar, except for gain at 13q13.3-q14.1 (log2 ratio ≤ 3), containing the STOML3, FREM2, and LHFP genes, which was restricted to the mesenchymal tumor area of a gliosarcoma. Further analyses of 64 cases of gliosarcoma using quantitative PCR showed amplification of the STOML3, FREM2 and LHFP genes in 14 (21%), 10 (15%), and 7 (11%) of mesenchymal tumor areas but not in glial tumor areas. Immunohistochemistry confirmed that STOML3 and FREM2 overexpression was more extensive in mesenchymal than in glial tumor areas. These results suggest that mesenchymal components in a small fraction of gliosarcomas may be derived from glial cells with additional genetic alterations.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3401. doi:1538-7445.AM2012-3401