IL-1 and IL-6 gene expression levels, normalized to GAPDH and expressed as Delta Ct values, were significantly increased by addition of MTX (1 uM) to 72 hour cultures of U937 cells and these increases were blocked by co-culture of MTX with PAR (1 uM) to levels that were not significantly different than those in control (CTRL) cultures (top two panels). P values for the gene expression comparisons were calculated by one-way ANOVA, and Dunnett’s post test showed that only the MTX cultures were significantly different (*P <0.05) from corresponding CTRL cultures. Furthermore, secreted IL-1 and IL-6 cytokines measured by ELISA in these 72 hour U937 supernatants were significantly decreased when cells were co-cultured with MTX and PAR (bottom two panels). Significance (P values) for the IL-1 and IL-6 supernatants was calculated by paired t test. ANOVA, analysis of variance; ELISA, enzyme-linked immunosorbent assay; IL, interleukin; MTX, methotrexate; PAR, parthenolide.