Expression and regulation of the transcriptional repressor ZNF43 in Ewing sarcoma cells

In vitro, cells derived from Ewing sarcoma (ES) with the characteristic somatic rearrangement between the genes EWS and FLII can be induced to differentiate toward a neuronal phenotype by exposure to agents such as dibutyryl cyclic AMP (db cAMP) or retinoic acid. Therefore, expression of the chimeric Ews-Flil protein does not irreversibly block the capacity of Ewing cells to engage in the neuronal differentiation program initiated by these agents. To identify genes that might be involved in the maintenance of Ewing cells in their undifferentiated state, a PCR-based differential display method was used to compare gene expression patterns in Ewing cell lines with those induced to differentiate toward a neuronal phenotype. A cDNA was expressed at high levels in proliferating Ewing-derived EW-1 cells and downregulated in EW-1 cells induced to differentiate, which corresponds to ZNF43, a multi-zinc finger protein containing the Krüppel-associated box (KRAB) transcriptional repression domain. Treatment of EW-1 cells with antisense oligonucleotides complementary to ZNF43 mRNA induces morphological differentiation and growth arrest. These findings suggest a role for ZNF43 in the maintenance of ES cells in an undifferentiated state, and that ZNF43 could be a primary target for differentiation stimuli in Ewing cells.