Abstract 66: CD99 functional analysis in glioblastoma by RNAseq
Authors: Oba-Shinjo Sueli M. , Cardoso Lais C. , Silva Roseli da , Lerario Antonio M. , Uno Miyuki , Marie Suely S.K. 
Published: August 2015

CD99 is a membrane protein expressed in a wide variety of normal tissues and implicated in several cellular physiologic processes, including haematopoietic cell differentiation, proliferation, diapedesis, cell-cell adhesion, migration, apoptosis induction, cellular architecture maintenance and transmembrane protein transport. Additionally, aberrant CD99 expression has been associated with numerous malignancies, including astrocytomas. Amongst astrocytomas of different malignant grades, glioblastoma (GBM) is the most aggressive and common of central nervous system tumors. Despite current multimodal therapies, including surgery, chemotherapy and radiotherapy, the median survival duration of patients is 17 months. We have previously demonstrated increased CD99 expression at mRNA and protein levels in astroctyoma of all malignant grades, with GBM showing the highest levels. Knocking down CD99 expression by siRNA efficiently decreased CD99 at mRNA and protein levels and concurrently decreased the migratory property of two GBM cell lines, U87MG and A172. We subsequently analysed the transcriptoma of both cell lines by RNA-seq in Illumina platform after transfection with siRNA for CD99 and compared to non-target control (NTC). CD99 gene and protein silencing was confirmed in both cell lines. A total of 413 and 340 genes for U87MG and A172, respectively, with expression ≤1.3 (p&lt;0.01, Bejamiini-Hochberg test) in knockdown condition in relation to NTC were detected, and they were analysed according to process networks using Metacore. A total of 129 genes had the expression diminished with CD99 in both cell lines, among them genes coding for proteins involved in migration and cytoskeletal remodelling, as expected. Also, we observed a decreased expression of genes involved in molecular mechanisms of translation control and protein folding regulation, as genes encoding for: subunits of the elongation factor-1 complex (EEF1A and EEF1A1), GTP-binding translation elongation factor (EEF2), several ribosomal proteins (PRPL4, RPL8, RPL15, RPL28, RPL32, RPL37A, RPS2, RPS3, RPS4, RPS6, RPS11 and RPS20), tRNA synthetase proteins (VARS and YARS), and heat shock proteins (HSC70, HSP70, HYOU1 and VCP). Furthermore, expression of MTOR, which encodes a common subunit protein of mTORC1 and mTORC2 complexes, is also downregulated with CD99 knockdown. Altogether, these results open insights for new roles of CD99 in GBM in controlling the regulation of translation, a crucial control of cell growth and proliferation. CD99 could thus be targeted to prevent protein translation in cancer cells.

Citation Format: Sueli M. Oba-Shinjo, Lais C. Cardoso, Roseli da Silva, Antonio M. Lerario, Miyuki Uno, Suely S.K. Marie. CD99 functional analysis in glioblastoma by RNAseq. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 66. doi:10.1158/1538-7445.AM2015-66