DKK1 and undifferentiated pleomorphic sarcoma: Using this rationale, we have previously shown that mesenchymal stem cells (MSCs) are the progenitors of malignant fibrous histiocytoma (MFH; now termed high grade undifferentiated pleomorphic sarcoma [HGUPS], a commonly diagnosed mesenchymal tumor) and that increased levels of DKK1, a Wnt developmental pathway inhibitor, mediate the transition from the MSC state to the MFH state [18].