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Brain Tumor Center and Departments of ¹ Pathology, ² Molecular Genetics, ³ Imaging Physics, and ⁴ Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas; and ⁵ Program in Genes and Development, University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas

Requests for reprints: Sadhan Majumder, Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 11, Houston, TX 77030. Phone: 713-792-8920; Fax: 713-792-6054. E-mail: majumder{at}mdanderson.org

Medulloblastoma, one of the most malignant pediatric brain tumors, is believed to arise from the undifferentiated external granule-layer cells in the cerebellum. It is a heterogeneous cancer, and the mechanism of tumorigenesis for the majority of types is unknown. Repressor element-1 silencing transcription/neuron-restrictive silencer factor (REST/NRSF) is a transcriptional repressor that can block transcription of a battery of neuronal differentiation genes by binding to a specific consensus DNA sequence present in their regulatory region. Previously, we found that some medulloblastoma cell lines express REST/NRSF at high levels compared with either neuronal progenitor cells or fully differentiated neurons. However, it is not known if REST/NRSF is indeed overexpressed in human medulloblastoma tumor specimens and in what frequency. Here, we did an immunohistochemical analysis of such tumor specimens using an anti-REST antibody. We show that among 21 human medulloblastoma tumors, 17 expressed REST/NRSF (6 strongly and 11 weakly). In contrast, adjacent normal cerebellum tissue sections and four of the tumor specimens did not express REST/NRSF, indicating that abnormal expression of REST/NRSF is observed in the majority of human medulloblastoma tumors. To determine whether countering REST/NRSF activity blocks tumorigenicity of medulloblastoma cells, especially in the intracranial (i.c.) environment, we found that adenovirus-mediated expression of REST-VP16, a recombinant transcription factor that can compete with REST/NRSF and activate REST/NRSF target genes instead of repressing them, blocked the i.c. tumorigenic potential of medulloblastoma cells and inhibited growth of established tumors in nude mice, suggesting that REST/NRSF may serve as a therapeutic target for medulloblastoma and that forced expression of neuronal differentiation genes in medulloblastoma cells through agents, such as REST-VP16, can interfere with their tumorigenicity.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Note: G.N. Fuller, X. Su, and R.E. Price contributed equally to this work. Current address of Z.R. Cohen: Department of Neurosurgery, Sheba Medical Center, Tel Hashomer 52621, Israel.

Received 8/31/04; revised 1/13/05; accepted 1/17/05.