FYN and synovial sarcoma: In fact, the elevated levels of FYN have been found in response to HDAC inhibitor-induced SS18-SSX protein degradation, and blocking FYN kinase activity with the small molecule PP2 can substantially enhance (about 10- to 30-fold) the sensitivity of synovial sarcoma cells to the clinically-applicable HDAC inhibitor FK228 in a dose-dependent fashion [37].