To corroborate the in vitro findings further, we examined the effect of serum samples obtained from RA patients, before treatment and after 6 months of tofacitinib treatment, for their ability to induce endostatin generation and affect MMP-9 and proteasome 20S activities when added to cultured HT1080 cells. The gene discussed is COL18A1; the disease is rheumatoid arthritis.