MMP9 and rheumatoid arthritis: STRING PPI analysis placed the 15 targets within a dense inflammatory backbone centred on TNF, IL1B, IL6, IL17A, TNFRSF1A, IL6R, JAK1/JAK2, IKBKB, MMP3/MMP9, PTGS2 and NOS2 nodes that integrate cytokine–cytokine receptor interaction, TNF, IL-17, JAK–STAT, NF-κB, rheumatoid arthritis (hsa05323) and arachidonic-acid pathways.