PTHLH and neoplasm: Additionally, TGF-β1 may autonomously promote metastasis, as the expression of a dominant-negative mutant of TGF-βR-II in the TNBC cell line MDA-MB-231 was reported to inhibit experimental bone metastases, whereas the overexpression of constitutively active TGF-βR-I increased the production of parathyroid hormone-related protein by the tumor cells and enhanced bone metastases (33).