Ewing sarcoma (EwS) is a pediatric bone cancer, which is characterized by the expression of chimeric fusion protein EWSR1-FLI1. Metastatic or relapsed EwS responds poorly to treatment. Thus, new therapies are needed. A potential target for therapy is chromosome instability (CIN) in EwS cells. These cells display frequent chromosome gains or losses due to CIN. How CIN occurs in EwS is unknown. CENP-A is an essential component of the centromere, the chromosome locus that mediates chromosome segregation. Neocentromeres (newly created centromeres at non-centromeric regions) or dysfunctional centromeres promote CIN. Our goal is to learn how centromere dysfunction leads to CIN in EwS, and our hypo...

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Ewing sarcoma (EwS) is a pediatric bone cancer, which is characterized by the expression of chimeric fusion protein EWSR1-FLI1. Metastatic or relapsed EwS responds poorly to treatment. Thus, new therapies are needed. A potential target for therapy is chromosome instability (CIN) in EwS cells. These cells display frequent chromosome gains or losses due to CIN. How CIN occurs in EwS is unknown. CENP-A is an essential component of the centromere, the chromosome locus that mediates chromosome segregation. Neocentromeres (newly created centromeres at non-centromeric regions) or dysfunctional centromeres promote CIN. Our goal is to learn how centromere dysfunction leads to CIN in EwS, and our hypothesis is that EWSR1-FLI1 promotes centromere dysfunction, a crucial driver of CIN. Aim 1: Determine how EWSR1-FLI1 induces CIN in EwS cells. CENP-A is increased in EwS cells, and EWSR1-FLI1 induces CENP-A expression. Thus, we hypothesize that increased CENP-A is a major driver of CIN in EwS cells. We will determine if reduction of CENP-A suppresses CIN in EwS. We found neocentromeres in EwS cells. How neocentromere occurs be characterized. As we found that both EWSR1 and EWSR1-FLI1 interact with CENP-A and that EWSR1 depletion reduces CENP-A deposition at the centromere, we will determine if EWSR1-FLI1 induces CIN by inhibiting EWSR1 in EwS. We thus will test if EWSR1 overexpression can suppress CIN. We will test if EWSR1-FLI1 can induce neocentromeres at EWSR1-FLl1 binding sites on the genome. Aim 2: To test the hypothesis that suppressing CIN can suppress drug resistance and metastasis in EwS. We will directly test the role of CIN in supporting drug resistance and metastasis by silencing CENP-A or overexpressing EWSR1 in EwS cells and mouse tumor models. Impact: This research will identify the molecular mechanism of CIN in EwS. Since CIN leads to cancer evolution, our research may provide novel avenues for new approaches to prevent drug resistance or metastasis in EwS.

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