PTGES3 and fibrosarcoma: Given the interactions between p23 and HSP90 and the fact that p23 as well as HSP90 has been found in conditioned media of fibrosarcoma cells (Eustace and Jay, 2004), it is plausible to infer that p23 is also indirectly involved in these processes through its role as an HSP90 co‐chaperone.