PTHLH and breast cancer: Lindemann reported that PTHrP expression was regulated by transforming growth factor β through Smad/ets synergism in MDA-MB-231 breast cancer cells [38], but in MCF-7 breast cancer cells, it was shown that PTHrP appeared to function as a osteolytic factor associated with breast cancer metastases via the Smad and MAPK (Mitogen-activated Protein Kinase) signaling pathways [39].