Critical role of zinc finger protein 521 in the control of growth, clonogenicity and tumorigenic potential of medulloblastoma cells

Raffaella Spina,Tiziana Mega,Charles G Eberhart,Gessica Filocamo,Stefania Scicchitano,Heather M Bond,Simonetta Pazzaglia,Maria Mesuraca,Samantha Semenkow,Marcel Kool,Michela Lupia,Christian Steinkühler,Emanuela Chiarella,Stefan Pfister,Daniela Pelaggi,Giovanni Morrone,Eli E Bar,Enrico Iaccino,Francesca Bernaudo

doi:10.18632/oncotarget.1176

Abstract

The stem cell-associated transcription co-factor ZNF521 has been implicated in the control of hematopoietic, osteo-adipogenic and neural progenitor cells. ZNF521 is highly expressed in cerebellum and in particular in the neonatal external granule layer that contains candidate medulloblastoma cells-of-origin, and in the majority of human medulloblastomas. Here we have explored its involvement in the control of human and murine medulloblastoma cells. The effect of ZNF521 on growth and tumorigenic potential of human medulloblastoma cell lines as well as primary Ptc1-/+ mouse medulloblastoma cells was investigated in a variety of in vitro and in vivo assays, by modulating its expression using lentiviral vectors carrying the ZNF521 cDNA, or shRNAs that silence its expression. Enforced overexpression of ZNF521 in DAOY medulloblastoma cells significantly increased their proliferation, growth as spheroids and ability to generate clones in single-cell cultures and semisolid media, and enhanced their migratory ability in wound-healing assays. Importantly, ZNF521-expressing cells displayed a greatly enhanced tumorigenic potential in nude mice. All these activities required the ZNF521 N-terminal motif that recruits the nucleosome remodeling and histone deacetylase complex, which might therefore represent an appealing therapeutic target. Conversely, silencing of ZNF521 in human UW228 medulloblastoma cells that display high baseline expression decreased their proliferation, clonogenicity, sphere formation and wound-healing ability. Similarly, Zfp521 silencing in mouse Ptc1-/+ medulloblastoma cells drastically reduced their growth and tumorigenic potential. Our data strongly support the notion that ZNF521, through the recruitment of the NuRD complex, contributes to the clonogenic growth, migration and tumorigenicity of medulloblastoma cells.

Highlights

Zinc finger protein 521 (EHZF/ZNF521) is a transcription co-factor originally identified for its abundant and selective expression in early progenitors of the human hematopoietic system [1]
Western blotting analysis of 5 medulloblastoma specimens in comparison with nonneoplastic cerebellar tissue confirmed the presence of equivalent amounts of ZNF521 protein (Fig 1 B)
A variety of dysregulated mechanisms are believed to contribute to its pathogenesis and to the homeostasis of the malignant cell population [41,42,43,44]; the existence of multiple major pathogenetic mechanisms is mirrored by the existence of distinct MB subgroups characterised by specific gene expression profiles [23,24,25,26,27,28,29,30,31, 45]

Summary

Introduction

Zinc finger protein 521 (EHZF/ZNF521) is a transcription co-factor originally identified for its abundant and selective expression in early progenitors of the human hematopoietic system [1]. ZNF521 contains 30 zinc fingers and an N-terminal motif of 12 amino acids that this factor shares with numerous transcriptional co-repressors [1, 2] most of which are endowed with a recognized regulatory role in diverse developmental processes. This motif recruits the nucleosome remodeling and histone deacetylase (NuRD) complex [3, 4] and is required for the co-repressor function of Friend of GATA (FOG)-1 [5, 6], SALL1 [7] and SALL4 [8]. Zfp521 has been implicated in the development of B-lymphoid malignancies including B-cell lymphomas [11] and acute B-cell leukemias – the latter in co-operation with the E2A-HLF fusion oncogene [12]

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Results

Conclusion