Furthermore, PIT1 co-localized with TXNDC5 is required for ER homeostasis, chondrocyte survival, and skeletal development [197], also TXNDC5 knockdown is highly toxic to osteosarcoma cells, possibly implying that it has a critical function in cells that endogenously express collagen-I [198]. Here, TXNDC5 is linked to osteosarcoma.