An example is the tumour suppressor PTEN, the low expression of which at sites of synovial invasion and growth has been described by Pap et al. [19] SLIT3 specifically, along with other SLIT/ROBO family members, is inactivated by promoter hypermethylation in multiple human cancers [20], and antagonizes invasiveness of RA synovial fibroblasts [21]. Here, PTEN is linked to rheumatoid arthritis.