LIN28B underlies the pathogenesis of a subclass of Ewing sarcoma

Ewing sarcoma (EwS) is associated with poor prognosis despite current multimodal therapy. Targeting of EWS-FLI-1, the fusion protein responsible for its pathogenesis, and its principal downstream targets has not yet produced satisfactory therapeutic options, fuelling the search for alternative approaches. Here, we show that the oncofoetal RNA-binding protein Lin28B regulates the stability of EWS-FLI-1 mRNA in about 10% of EwS. Lin28B depletion in these tumours leads to a decrease in expression of EWS-FLI-1 and its direct transcriptional network, abrogating EwS cell self-renewal and tumorigenicity. Moreover, pharmacological inhibition of Lin28B mimics the effect of Lin28B depletion, suggesting that Lin28B sustains the emergence of a subset of EwS in which it also serves as an effective therapeutic target. Four samples of spherogenic cultures from primary Ewing sarcomas