title: Effect of infliximab on mRNA expression profiles in synovial tissue of rheumatoid arthritis patients.
abstract: We examined the gene expression profiles in arthroscopic biopsies retrieved from 10 rheumatoid arthritis patients before and after anti-TNF treatment with infliximab to investigate whether such profiles can be used to predict responses to the therapy, and to study effects of the therapy on the profiles. Responses to treatment were assessed using European League Against Rheumatism response criteria. Three patients were found to be good responders, five patients to be moderate responders and two patients to be nonresponders. The TNF-alpha status of the biopsies from each of the patients before treatment was also investigated immunohistochemically, and it was detected in biopsies from four of the patients, including all three of the good responders. The gene expression data demonstrate that all patients had unique gene expression signatures, with low intrapatient variability between biopsies. The data also revealed significant differences between the good responding and nonresponding patients (279 differentially expressed genes were detected, with a false discovery rate < 0.025). Among the identified genes we found that MMP-3 was significantly upregulated in good responders (log2 fold change, 2.95) compared with nonresponders, providing further support for the potential of MMP-3 as a marker for good responses to therapy. An even more extensive list of 685 significantly differentially expressed genes was found between patients in whom TNF-alpha was found and nonresponders, indicating that TNF-alpha could be an important biomarker for successful infliximab treatment. Significant differences were also observed between biopsies taken before and after anti-TNF treatment, including 115 differentially expressed genes in the good responding group. Interestingly, the effect was even stronger in the group in which TNF-alpha was immunohistochemically detected before therapy. Here, 1,058 genes were differentially expressed, including many that were novel in this context (for example, CXCL3 and CXCL14). Subsequent Gene Ontology analysis revealed that several 'themes' were significantly over-represented that are known to be affected by anti-TNF treatment in inflammatory tissue; for example, immune response (GO:0006955), cell communication (GO:0007154), signal transduction (GO:0007165) and chemotaxis (GO:0006935). No genes reached statistical significance in the moderately responding or nonresponding groups. In conclusion, this pilot study suggests that further investigation is warranted on the usefulness of gene expression profiling of synovial tissue to predict and monitor the outcome of rheumatoid arthritis therapies.
authors.affiliation: School of Biotechnology, Department of Gene Technology, AlbaNova University Center, Royal Institute of Technology, Stockholm, Sweden. johanl@biotech.kth.se
authors.forename: Johan
authors.initials: J
authors.lastname: Lindberg
authors.forename: Erik
authors.initials: E
authors.lastname: af Klint
authors.forename: Anca Irinel
authors.initials: AI
authors.lastname: Catrina
authors.forename: Peter
authors.initials: P
authors.lastname: Nilsson
authors.forename: Lars
authors.initials: L
authors.lastname: Klareskog
authors.forename: Ann-Kristin
authors.initials: AK
authors.lastname: Ulfgren
authors.forename: Joakim
authors.initials: J
authors.lastname: Lundeberg
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D020869:Gene Expression Profiling; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D010865:Pilot Projects; D012333:RNA, Messenger / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab