BIRC5 and synovial sarcoma: In this study, the increased levels of PKR, p-PKR, PERK, p-PERK/PERK ratio, eIF2α, p-eIF2α, ATF4, and ATF4-target genes such as xCT, survivin and CHOP determined by Western blot, as well as staining by immunofluorescence, indicated increased activation of the ISR in acinar cells of LSGs from SS-patients.