PinX1 inhibits telomerase activity in gastric cancer cells through Mad1/c-Myc pathway.
BACKGROUND
The aim of this study was to investigate the role of Mad1/c-Myc in telomerase regulation in gastric cancer cells in order to gain insight into telomerase activity and to evaluate PinX1 as a putative inhibitor of gastric cancer.


METHODS
PinX1 and PinX1siRNA eukaryotic expression vectors were constructed by recombinant technology and transfected into gastric carcinoma cells using Lipofectamine 2000. Telomerase activity was measured by the telomeric repeat amplification protocol. Apoptosis of gastric cancer cells was analyzed by flow cytometry and transmission electron microscopy. Reverse transcription-polymerase chain reaction and Western blotting were used to assess the expression levels of PinX1 and Mad1/c-Myc.


RESULTS
We found that PinX1-negative gastric cancer cells showed significantly higher telomerase activity than did the PinX1-postive cells. PinX1-transfection reduced telomerase activity in PinX1-negative gastric cancer cells and exhibited an upregulation of Mad1 and downregulation of c-Myc expression. Pinx1 RNAi treatment led to downregulation of Mad1 and upregulation of c-Myc.


CONCLUSIONS
Suppression of telomerase activity mediated by PinX1 is involved in the Mad1/c-Myc pathway.
Wang
Hong-bin
HB
Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
Wang
Xing-wei
XW
Zhou
Gang
G
Wang
Wei-qiang
WQ
Sun
Yong-gang
YG
Yang
Shi-ming
SM
Fang
Dian-chun
DC
D017209:Apoptosis; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005434:Flow Cytometry; D005753:Gastric Mucosa / Q000378:metabolism / Q000648:ultrastructure; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc; D006801:Humans; D046529:Microscopy, Electron, Transmission; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C501384:MAD1L1 protein, human; C116115:MYCBP protein, human; D009687:Nuclear Proteins; C440808:PINX1 protein, human; D012334:RNA, Neoplasm; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D019098:Telomerase