A newly human developed diabody against CD99 delivers a lethal signal through p53 pathway reactivation in Ewing sarcoma cells and synergistically acts with doxorubicin

We present here a new engeneered human bivalent single chain fragment variable diabody (C7 scFv diabody) directed against CD99, a transmembrane protein whose high expression characterizes Ewing sarcoma. The triggering of CD99 with C7scFv diabody induces rapid and massive Ewing sarcoma cell death through MDM2 ubiquitination and p53 reactivation. Accordingly, the most CD99-responsive Ewing sarcoma cells have transcriptional active p53 and greatly benefit from MDM2 degradation. CD99 triggering also potentiates the cytotoxic effect of doxorubicin in vitro and in vivo and reactivates p53 to a much greater degree, which in turn markedly increased expression of pro-apoptosis genes. Evaluation of Ki-67 labelling and apoptosis rate by TUNEL confirms the efficacy of the treatment in xenografts. In contrast, mesenchymal stem cells, though expressing high levels of CD99, show no p53 activation and escape death induced by CD99 C7scFv diabody. No sign of toxicity was observed in mice treated with anti-CD99 scFV C7 diabody. Overall, our data provide the rationale for the use of this newly developed anti-CD99 diabody in the treatment of patients with Ewing sarcoma.
Source: New Horizons in Translational Medicine - Category: Research Source Type: research