PRG4 and chondrosarcoma: To begin to determine whether Creb5 can confer competence for Prg4 expression in growth plate-like chondrocytes, we infected either a human chondrosarcoma cell line (SW1353) or an immortalized human costal chondrocyte cell line (C-28/I2;49) with lentivirus encoding either EGFP or Creb5.