Abstract 4353: Identification of proteins regulated by mTOR in brain tumors of patients with tuberous sclerosis complex

Abstract

Abstract Tuberous sclerosis complex (TSC) is characterized by the formation of benign tumors in many organs (mainly brain, heart, kidneys, skin or lungs) and is often associated with epilepsy, mental retardation and autism. Brain lesions include subependymal giant cell astrocytomas (SEGAs), low-grade tumors of a mixed glioneuronal lineage, which are the major cause of morbidity in children and young adults with TSC. The disease is caused by mutations in tumor suppressor genes: TSC1 (Hamartin) or TSC2 (Tuberin) leading to enhancement of mammalian Target Of Rapamycin (mTOR) kinase activity, deregulation of cell growth and tumorigenesis. Signaling via mTOR participates in complex genomic responses but its effectors in the brain are largely unknown. Therefore, we performed first genome-wide expression profiling on SEGAs using Affymetrix Human Genome arrays. We identified differentially expressed specific genes involved in tumorigenesis (up-regulated) and the nervous system development (down-regulated) in SEGAs and SEGA-derived cell cultures when compared to the normal brain or cultured human astrocytes. Out of genes differentially expressed in TSC, 11 were validated by real time PCR on independent tumor samples and 3 SEGA-derived cultures. Immunohistochemistry on paraffin-embedded sections confirmed up-regulated levels of several identified proteins in SEGAs. ANXA1, GPNMB, LTF, RND3, S100A11, SFRP4 and NPTX1 were shown to be mTOR effector genes in SEGA, as their expression was modulated by an mTOR inhibitor - rapamycin in SEGA-derived cell cultures. We are currently investigating the role of ANXA1, GPNMB and S100A11 in regulation of cell viability, migration, adhesion, size and shape of cultured SEGA cells using RNA interference. Furthermore, we observed that combined pharmacological inhibition of mTOR and extracellular signal regulated kinase (ERK) signaling pathways in SEGA cells affected their viability (MTT metabolism test), proliferation (BrdU assay), migration (scratch assay), morphology and size (volume, area and height measured with confocal microscopy). For the first time, we identified genes related to the occurrence of SEGA and regulated by mTOR, and showed an effective modulation of SEGA growth by inhibition of both mTOR and ERK signaling pathways, which could represent a novel therapeutic approach. The study was supported by Ministry of Science and Higher Education grant N N301 263536. 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 4353.