STAT3 and neoplasm: We provide some evidence in support of this by demonstrating that exogenous expression of a Stat3 dominant negative (Y705F) during tumor initiation with ACVR1 R206H; PDGF-A; and p53 loss results in downregulation of two mesenchymal genes that were upregulated by ACVR1 R206H in vitro, namely vimentin and tenascin C.