Mutations in mitochondrial control region DNA in gastric tumours of Japanese patients.

The non-coding control region of mitochondrial DNA (mtDNA), containing the hypervariable regions HV1 and HV2 and the D-loop region, was screened for mutations in 45 gastric tumours (15 tumours each of adenoma, differentiated adenocarcinoma and undifferentiated carcinoma). We found mutations in two of the 45 tumours (4%); a 1 bp A deletion at nucleotide position 248 in a differentiated adenocarcinoma and a G to A transition at nucleotide position 16,129 in an adenoma. We also observed 10 polymorphisms, four of which were not previously recorded. Both mtDNA mutations were present in replication error negative (RER-) tumours. Short mono- or dinucleotide repeats in the control region, such as (C)7, (A)5 or (CA)5, were not altered regardless of nuclear genetic instability. In summary, mtDNA is mutated in a subset of benign and malignant gastric tumours, but, disruption of the mtDNA repair system appears not to be significantly involved in gastric tumours of Japanese patients.