EP300 and rheumatoid arthritis: Furthermore, we also confirmed that activation of PI3K by 740Y‐P alleviated the inhibitory effect of ATT on the proliferation, migration and invasion, and apoptosis‐inducing effect of ATT in RA‐FLSs (Figure 6R–Y), suggesting that PI3K/AKT/p300 signalling is essential for ATT‐induced inhibition of abnormal functions in RA‐FLSs.