Abstract 5050: KCNJ2 constitutes a marker and therapeutic target of high-risk medulloblastomas.
Authors: Valdora Francesca , Freier Florian , Garzia Livia , Ramaswamy Vijay , Seyler Claudia , Hielscher Thomas , Brady Nathan , Northcott Paul A. , Kool Marcel , Jones David TW , Witt Hendrik , Tonini Gian Paolo , Scheurlen Wolfram , Katus Hugo A. , Kulozik Andreas E. , Zitron Edgar , Korshunov Andrey , Lichter Peter , Taylor Michael D. , Pfister Stefan M. , Remke Marc 
Published: August 2014

Abstract
Medulloblastoma comprises the most common malignant brain tumor in children. Non-WNT/SHH tumors define the most refractory medulloblastoma subgroups. Interestingly, 17q gain, the most common genetic aberration in medulloblastoma, comprises a cytogenetic hallmark of these molecular high-risk tumors detected in group 3 (62%), and group 4 (73%). The majority of recurrent tumors harbor 17q gain in the corresponding primary. Virtually all of these tumors develop resistance to current treatment protocols at relapse. The lack of a common molecular target hampers the development of urgently needed novel treatment strategies.
Through mRNA expression profiling of 64 primary tumor samples, we identified potassium inwardly-rectifying channel J2 (KCNJ2) as one of the most upregulated genes on chromosome 17q in tumors with 17q gain. High KCNJ2 transcript levels were significantly associated with non-WNT/non-SHH grouping, anaplastic histology, metastatic dissemination, and poor clinical outcome. KCNJ2 protein expression was analyzed by immunohistochemistry in a large cohort of patients (n=199), and high protein expression levels were found to be strongly correlated with 17q gain, metastatic dissemination, and inferior prognosis (p&lt;0.0001). To functionally validate the potential role of KCNJ2 in medulloblastoma biology, we performed knockdown experiments by small interfering RNA-mediated silencing in two well-characterized medulloblastoma cell lines. Transient knockdown of KCNJ2 resulted in a reduced proliferation rate and induction of apoptosis. Furthermore, treatment of the medulloblastoma cell lines and medulloblastoma stem cells with amiodarone and gambogic acid, two inhibitors of this class of Kir channels, phenocopied these effects in a time- and dose-dependent manner. Whole cell patch clamp results revealed a nearly complete current blockade upon inhibitor treatment. Subsequently, we showed that pharmacological inhibition of KCNJ2 and knockdown KCNJ2 significantly reduced tumor growth and resulted in prolonged survival in an orthotopic medulloblastoma mouse model.
In summary, our data suggest that pharmacological inhibition of KCNJ2 may constitute a new therapeutic option for patients with high-risk medulloblastomas.
Citation Format: Francesca Valdora, Florian Freier, Livia Garzia, Vijay Ramaswamy, Claudia Seyler, Thomas Hielscher, Nathan Brady, Paul A. Northcott, Marcel Kool, David TW Jones, Hendrik Witt, Gian Paolo Tonini, Wolfram Scheurlen, Hugo A. Katus, Andreas E. Kulozik, Edgar Zitron, Andrey Korshunov, Peter Lichter, Michael D. Taylor, Stefan M. Pfister, Marc Remke. KCNJ2 constitutes a marker and therapeutic target of high-risk medulloblastomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5050. doi:10.1158/1538-7445.AM2013-5050