ATF6 and rheumatoid arthritis: Apoptosis induction resulting from exposure to ER stress inducers [thapsigargin (Tg) and tunicamycin (Tm)] became more obvious when ATF6α was silenced or inactivated in RA FLSs (Figure 2D; Supplementary Figure 2D), which was also reflected by the increase of Cleaved-caspase3 (CASP3) and B-cell lymphoma-2 associated x protein (Bax) but decrease in B-cell lymphoma-2 (BCL-2) expression (Figure 2E).