Berning, Philipp; Schäfer, Christiane; Clemens, Dagmar; Korsching, Eberhard Ulrich; Dirksen, Uta; Potratz, Jenny Charlotte: The CXCR4 antagonist plerixafor (AMD3100) promotes proliferation of Ewing sarcoma cell lines in vitro and activates receptor tyrosine kinase signaling