ERN1 and osteosarcoma: DDRGK1 has been reported to induce ER stress and enhance ER stress‐induced apoptosis in cancer cells by regulating IRE1a‐XBP1 signaling.[12, 17] To further confirm the role of DDRGK1 in osteosarcoma cell apoptosis, we used the ER stress‐related apoptosis inducer thapsigargin (Tg).[28] We observed a Tg‐induced time‐dependent inhibition of proliferation.