In addition, recent accumulating lines of experimental evidence have also revealed that PC stem/progenitor cells, also designated as PC- and metastasis-initiating cells, expressing stem cell-like markers such as CD133, CD44high, aldehyde dehydrogense “ALDHhigh” and/or CXC chemokine receptor 4 can provide critical functions in prostate carcinogenesis, metastases at distant sites and tumor re-growth and disease recurrence after treatment initiation [4], [10], [13], [14], [40]–[58]. The gene discussed is PROM1; the disease is pachyonychia congenita.