EIF2AK3 and synovial sarcoma: The combination of quisinostat and bortezomib elicits high expression of ER stress markers in synovial sarcoma cell lines, as demonstrated by the activation of: phosphorylated-PERK (slows translation [28]), IRE1α (unfolded protein response element involved in ER chaperone upregulation and stress recovery [29]), BiP (molecular chaperone [30]), phosphorylated-JNK (c-Jun N-terminal kinases, activated in response to cellular stress [31]) and CHOP (DDIT3, pro-apoptotic protein [32]) (Fig 5D).