Mutations of mitochondrial 12S rRNA in gastric carcinoma and their significance.
OBJECTIVE
To detect the variations of mitochondrial 12S rRNA in patients with gastric carcinoma, and to study their significance and the relationship between these variations and the genesis of gastric carcinoma.


METHODS
PCR amplified mitochondrial 12S rRNA of 44 samples including 22 from gastric carcinoma tissues and 22 from adjacent normal tissues, was detected by direct DNA sequencing. Then laser capture microdissection technique (LCM) was used to separate the cancerous cells and dysplasia cells with specific mutations. Denaturing high performance liquid chromatography (DHPLC) plus allele-specific PCR (AS-PCR), nest-PCR and polyacrylamide gel electrophoresis (PAGE) were used to further evaluate this mutant property and quantitative difference of mutant type between cancerous and dysplasia cells. Finally, RNAdraw biosoft was used to analyze the RNA secondary structure of mutant-type 12S rRNA.


RESULTS
Compared with Mitomap database, some new variations were found, among which np652 G insertion and np716 T-G transversion were found only in cancerous tissues. There was a statistic difference in the frequency of 12S rRNA variation between intestinal type (12/17, 70.59%) and diffusive type (5/17, 29.41%) of gastric carcinoma (P<0.05). DHPLC analysis showed that 12S rRNA np652 G insertion and np716 T-G transversion were heteroplasmic mutations. The frequency of 12S rRNA variation in cancerous cells was higher than that in dysplasia cells (P<0.01). 12S rRNA np652 G insertion showed obviously negative effects on the stability of 12S rRNA secondary structure, while others such as T-G transversion did not.


CONCLUSIONS
The mutations of mitochondrial 12S rRNA may be associated with the occurrence of intestinal-type gastric carcinoma. Most variations exist both in gastric carcinomas and in normal tissues, and they might not be the characteristics of tumors. However, np652 G insertion and np716 T-G transversion may possess some molecular significance in gastric carcinogenesis. During the process from normality to dysplasia, then to carcinoma, 12S rRNA tends to convert from homoplasmy (wild type) to heteroplasmy, then to homoplasmy (mutant type, np717 T-G).
Han
Cheng-Bo
CB
Cancer Institute, the First Affiliated Hospital, China Medical University, Shenyang 110001, Liaoning Province, China.
Ma
Jia-Ming
JM
Xin
Yan
Y
Mao
Xiao-Yun
XY
Zhao
Yu-Jie
YJ
Wu
Dong-Ying
DY
Zhang
Su-Min
SM
Zhang
Yu-Kui
YK
D001483:Base Sequence; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D017354:Point Mutation; D012313:RNA / Q000737:chemistry / Q000235:genetics*; D000077278:RNA, Mitochondrial; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics*; D013274:Stomach Neoplasms / Q000145:classification / Q000235:genetics* / Q000473:pathology
D000077278:RNA, Mitochondrial; D012335:RNA, Ribosomal; C075526:RNA, ribosomal, 12S; D012313:RNA