C-myc antisense oligodeoxynucleotides can induce apoptosis and down-regulate fas expression in rheumatoid synoviocytes

Objective. To investigate the role of c-myc in the pathogenesis of rheumato id arthritis (RA) and the mechanism of synovial apoptosis. Methods. Using cultured human synoviocytes from patients with RA and c-myc antisense oligodeoxynucleotides (AS ODN), we examined the inhibition of cel l proliferation by the MTI assay and the induction of apoptosis with TUNEL staining and fluorescence microscopy, In addition, the effect of c-myc on d ownregulation of Fas expression was analyzed by now cytometry, cytotoxicity assay, and reverse transcriptase-polymerase chain reaction. Results. Treatment with c-myc AS ODN induced inhibition of cell proliferati on, along with downregulation of c-Myc protein and c-myc messenger RNA (mRN A) expression. The morphologic changes of synovial cell death were typical of apoptosis. In addition, c-myc AS ODN treatment down-regulated expression of Fas mRNA but not Fas antigen. Analysis of the involvement of the caspas e cascade revealed that the cytotoxic activity of c-myc AS ODN was complete ly blocked by inhibitors of both caspase 1 (YVAD-FMK) and caspase 3 (DEVD-F MK). Conclusion. Our results strongly suggest that c-myc AS ODN might be a usefu l therapeutic tool in RA and clarify that cell death by c-myc AS ODN is ind uced through the caspase cascade, similar to Fas-induced apoptosis, In addi tion, combination therapy with anti-Fas antibody and c-myc AS ODN reduced F as-dependent cytotoxicity.