PROM1 and fibrosarcoma: PCI has been used to successfully target cells expressing CD133, a surface molecule which has been described as a marker for stem‐like cancer cells exhibiting resistance to chemotherapeutic agents and resulting in a poor prognosis.43, 52 Fibrosarcoma and liposarcoma cells in vitro were exposed to saporin bound to antibodies against two different epitopes of CD133, combined with TPCS2a and light.43 Administration of anti‐CD133 caused some cytotoxicity on its own, which could be related to iron uptake pathways and induction of dedifferentiation in cells.