Background Tocilizumab (TCZ), a humanised anti-interleukin (IL)6 receptor antibody, was shown to be therapeutically effective in RA patients but the biological effect of TCZ on the immune response was not fully understood. DNA microarray can be amenable to exhaustively analyse the gene expression (GE) including immune response related genes.
Objectives To investigate the effect of TCZ on the immune response related GE profiles and to elucidate the changes of immune response functions in RA patients before and after treatments.
Methods Two-color microarray was performed by using whole blood samples here. The baseline GE profiles of the 112 RA patients in the Japanese phase III SATORI study (1), in which active RA patients were allocated to receive either TCZ 8mg/kg every 4 weeks (TCZ group: 54 patients) or MTX 8mg/week (MTX/control group: 58 patients) for 24 weeks, and 45 healthy individuals (HI) were obtained. The effect of treatments was investigated by directly comparing the samples before versus after the treatment. Each investigation was performed in duplicate with DNA labeling color reversal (dye swap). The average values of log2 (after/before) were used for further analysis. The genes with median expression levels of 1.2-fold changed after TCZ treatment were functionally categorized using Expression Analysis Systematic Explorer (EASE) version 2.0 bioinformatics software. Significant differences of GE levels between 112 RA at baseline and 45 HI, and between 54 TCZ and 58 MTX treated RA patients were defined by Mann-Whitney test.
Results The expressions of 491 genes were identified to have 1.2-fold changed in TCZ group. EASE analysis revealed that these genes mainly related to protein biosynthesis (EASE Score =1.64E-41), ribosome biogenesis (4.23E-10), and response to biotic stimulus (4.19E-04). 44 genes out of the 45 genes categorized to response to biotic stimulus were included in defense response category, in which 36 genes also belonged to immune response category. Arachidonate 5-lipoxygenase-activating protein, defensin alpha (DEFA)3, DEFA4, complement component 8 gamma polypeptide, platelet factor 4 (chemokine (C-X-C motif) ligand 4), pro-platelet basic protein (chemokine (C-X-C motif) ligand 7), S100A9, S100A12, IL-1 receptor type II, peptidoglycan recognition protein 1, and C-type lectin domain family 4 member E in this category were found significantly overexpressed in RA patients before TCZ treatment when compared to HI. Most remaining other genes such as major histocompatibility complex (MHC) class II molecules (HLA-DPA1, HLA-DPB1, HLA-DPQA1, HLA-DPQB1, HLA-DRA, and HLA-DMA), killer cell lectin-like receptor subfamily members (KLRB1, KLRD1, KLRK1, and KLRF1), granulysin, immunoglobulin J, and chemokine (C-C motif) ligand 5 were found significantly underexpressed. All the GEs were normalised after TCZ treatment whereas these were unchanged in MTX group.
Conclusions TCZ treatment normalised the expressions of immune response related genes in RA patients. The therapeutic effect of TCZ may be partly contributed by normalisation of these genes.
Nishimoto N, et al. Mod Rheumatol. 2009;19:12-9
Disclosure of Interest N. Nishimoto Grant/Research support from: Chugai Pharamaceutical Co. Ltd., Consultant for: Chugai Pharamaceutical Co. Ltd., Roche group, H.-M. Lee: None Declared, M. Murakami: None Declared, C. Aoki: None Declared, Y. Li: None Declared, T. Matsutani: None Declared
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