Detection of somatic mutations in the mitochondrial DNA control region of colorectal and gastric tumors by heteroduplex and single‐strand conformation analysis

Abstract

Each entire hypervariable region of the mitochondrial DNA control region was screened for mutations from paired normal and tumor DNA corresponding to a group of 21 patients (13 colorectal and 8 gastric adenocarcinomas) using both heteroduplex analysis and single-strand conformation analysis. These two mutation scanning strategies allowed the identification of sequence alterations in 3/13 (23%) colorectal tumors and in 3/8 (37%) gastric tumors. Heteroduplex analysis showed the heteroplasmic state of the majority of these tumor mutations. Sequence analysis revealed two A:T/G:C transitions (nucleotide positions: 16241 and 16166) in hypervariable region 1 (HV1) and two C:G/T:A transitions (nucleotide positions: 76 and 312), one A:T/G:C transition (nucleotide position: 93), a 1-basepair C:G deletion (nucleotide position: 309), and a 2-base-pair CC:GG insertion (nucleotide position: 309) in the HV 2 region. A considerable proportion of these mutations was found in homopolymeric regions which are highly polymorphic among humans. Different mechanisms (clonal expansion, increased oxidative damage, and nuclear mutator mutations) were suggested to explain the increased mitochondrial DNA mutation rate observed in cancer.

Mutations in the mitochondrial DNA D-Loop region occur frequently in adenocarcinoma in Barrett's esophagus

“…Tamura et al (1999) analysed the mutations of the mtDNA D-Loop region including HV1 and HV2 in 45 Japanese patients with gastric cancer, and found mutations in 4% of the tumors. Conversely, Alonso et al (1997) detected mutations in the mtDNA D-Loop region in 23% colorectal tumors and 37% gastric tumors. Fliss et al (2000) analysed mutations in mtDNA in bladder, head and neck, and lung cancer.…”

“…Recently, mtDNA mutations were reported to occur in human cancers (Burgart et al, 1995;Alonso et al, 1997;Polyak et al, 1998;Tamura et al, 1999;Habano et al, 1999Habano et al, , 2000Fliss et al, 2000). Alonso et al (1997) detected mutations in the mtDNA displacementloop (D-Loop) region in colorectal and gastric malignancies.…”

“…Alonso et al (1997) detected mutations in the mtDNA displacementloop (D-Loop) region in colorectal and gastric malignancies. The D-Loop region is the major control site for mtDNA expression because it contains the leading-strand for origin of replication and major promoters for transcription (Taanman, 1999).…”

“…They detected mutations of mtDNA in 50% of cancers. In addition, 67% of T to C (310) C to T (308) T to C (310) C to G (314) T to C (310) C to T (311) 7 ( 7) ( 7) C to T (310) T to C (311) 8 ( 7) (Alonso et al, 1997). However, frequencies might vary between di erent tumor entities (Alonso et al, 1997;Fliss et al, 2000).…”

“…In addition, 67% of T to C (310) C to T (308) T to C (310) C to G (314) T to C (310) C to T (311) 7 ( 7) ( 7) C to T (310) T to C (311) 8 ( 7) (Alonso et al, 1997). However, frequencies might vary between di erent tumor entities (Alonso et al, 1997;Fliss et al, 2000). Fliss et al (2000) concluded that the detection of mtDNA mutations may provide a powerful molecular screening marker for the detection of cancer in bodȳ uids.…”