Exp Clin Endocrinol Diabetes 2012; 120 - P15
DOI: 10.1055/s-0032-1330100

Polycomb group repressive complex protein EZH2 regulates tight junction protein Claudin-1 in craniopharyngiomas

C Stache 1, A Hölsken 1, N Raffel 1, S Schlaffer 2, R Fahlbusch 3, M Buchfelder 2, I Blümcke 1, R Buslei 1
  • 1Department of Neuropathology, University Hospital Erlangen-Nuremberg, Erlangen, Germany
  • 2Department of Neurosurgery, University Hospital Erlangen-Nuremberg, Erlangen, Germany
  • 3International Neuroscience Institute, Hannover, Germany

Objectives: Craniopharyngiomas (CP) are benign, epithelial tumors of the sellar region, consisting of adamantinomatous (adaCP) and papillary (papCP) variants. AdaCP show enhanced migratory potential in cells with activated WNT signalling, and altered distribution of tight junction protein Claudin-1 (CLDN1). Claudins play a major role in cell polarity and cell adhesion. The aim of this study was to elucidate whether epigenetic regulators influence CLDN1 expression in CP. A possible candidate is the methyltransferase Enhancer of Zeste homolog 2 (EZH2), a member of the polycomb group repressive complex, which is differenzially expressed in many types of cancer and associated with gene repression. Methods: We analysed CLDN1 and EZH2 distribution patterns in CP (11 papCP, 40 adaCP) using immunohistochemistry and double immunofluorescence staining. Impact of EZH2 expression was explored by RNA interference (RNAi) in cell cultures of different tumor types (10 adaCP, 2 breast carcinoma, 2 colon carcinoma, 2 melanoma). Subsequently, real time PCR and western blot analyses were conducted to investigate EZH2 dependent CLDN1 expression levels. Results: Immunohistochemistry showed enhanced levels of EZH2 and reduced to absent expression of CLDN1 in β-catenin accumulating cell clusters of adaCP. Double immunofluorescence staining confirmed this assumption. In contrast, papCP displayed homogenous membranous CLDN1 staining with hardly detectable expression of EZH2. Down regulation of EZH2 caused significant increase of CLDN1 expression on mRNA and protein level. This result could be observed in adaCP as well as in malignant tumor entities like colon carcinoma, breast carcinoma and melanoma. Conclusion: EZH2 influences CLDN1 expression in adaCP and other malignant tumors, pointing to a general regulatory role. Further analyses are necessary to clarify the underlying mechanism e.g. direct methylation of CLDN1 or indirect inhibition via EZH2 targets.