In this regard, numerous growth factors and cytokines, including SDF-1, EGF, sonic hedgehog (SHH), TGF-β1, bone morphogenic proteins (BMPs) and MIC-1 released by metastatic PC cells, stromal fibroblasts, osteoblasts, osteoclasts and HSC/HPCs in BM microenvironment may contribute to the regulation of dormancy phenomenon of PC cells in hypoxic endosteal niche and promote their re-activation and formation of macrometastases and osteoblastic and/or osteolytic lesions under specific microenvironmental conditions [53, 194, 209, 215–217]. The gene discussed is SHH; the disease is pachyonychia congenita.