H-RAS ONCOGENE POINT MUTATIONS IN ARTHRITIC SYNOVIUM

Objective. To examine mutational activation of ras proto-oncogenes in synovial tissue from patients with rheumatoid arthritis (RA) compared with synovial specimens from patients with osteoarthritis (OA) or othe r arthropathies. Synovial samples from cadavers, without any signs of joint disease, were used as control material, Methods, Using a combina tion of polymerase chain reaction (PCR) and automated sequencing of th e amplified PCR product, regions around codons 12, 13, and 61 of the H -, K-, and N-ras proto-oncogenes were analyzed, Confirmation of mutati ons was based on restriction fragment length polymorphism analysis and /or oligonucleotide hybridization, Results, Four (6%) of 72 patients w ith RA, 2 (13%) of 16 with OA, and 1 (8%) of 12 with other arthropathi es harbored mutant H-ras proto-oncogenes, and were heterozygous at cod on 13 for the GGT-->GAT (Gly-->Asp) change, An unexpected mutation was found in the H-ras gene, in which a heterozygous GTG-->ATG (Val-->Met ) mutation was observed over codon 14. The incidence for this mutation was 39% (28 of 72) in RA patients, 91% (15 of 16) in OA patients, and 42% (5 of 12) in patients with other arthropathies. All samples carry ing the codon 13 mutation of H-ras were also codon 14-mutated, i.e., d ouble mutations existed, Identical point mutations were also detected in a few synovial specimens obtained from cadavers (n = 8), including a single case of double mutation, All specimens showed normal K-and N- ras loci. Conclusion. Activation of proto-oncogene H-ras by point muta tion in codons 13 and 14 occurred in the synovial tissue of patients w ith RA, OA, or other arthropathies, as well as, to some extent, in the control synovia, indicating that the phenomenon is not specific for R A, In codon 14, incidence of the H-ras point mutation was highest in O A tissue, The possible significance of this codon 14-mutated H-ras gen e needs to be clarified.