2000 年 29 巻 p. 29-36
It has been established that there are two isoforms of mammalian branched-chain aminotransferases, cytosolic (BCATc) and mitochondrial (BCATm). Since the BCATc was reported to be a direct target for c-Myc regulation, we investigated expression of mRNAs for c-myc, BCATc, and BCATm in human gastric cancer cells and tissues. MKN45 and KATOIII were used as human gastric cancer cell lines. Human gastric mucosal tissues with cancer were obtained from 9 patients and those with non-ulcer dyspepsia (NUD) were from 8 patients by endoscopic biopsy. Expression of mRNA was measured by the method of polymerise-chain reaction coupled with reverse transcription. Expression of c-myc mRNA was detected in both cell lines but was greater in MKN45. Expression of BCATc mRNA was detected in KATOIII, but not in MKN45, whereas expression of BCATm mRNA was detected only in MKN45. In the analyses of human gastric tissues, it was found that c-myc mRNA was expressed in all of the tissues examined, but overexpression of the mRNA was detected in the 5 tissues with cancer. On the other hand, expression of BCATc mRNA was detected in 4 tissues with gastric cancer, in which only one tissue had the overexpression of c-myc mRNA. Expression of BCATc mRNA was not detected in all tissues with NUD. BCATm mRNA expression was detected in all tissues with cancer or NUD. These results suggest that there is no correlation between expression of mRNAs for c-myc and BCATc in these tissues and that expression of BCATc in gastric cancer cells and tissues is regulated in a manner independent of c-myc expression.
