Retinoic acid receptor beta is required for anti-activator protein-1 activity by retinoic acid in gastric cancer cells.
OBJECTIVE
To investigate the role of retinoic acid receptor beta (RARbeta) in mediating inhibitory effect of all-trans retinoic acid (ATRA) on activator protein-1 (AP-1) activity in gastric cancer cells.


METHODS
Transient transfection and chloramphenicol acetyltransferase (CAT) assay, Nort hern blot, gene transfection, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and anchorage independent growth assay were used.


RESULTS
Transient transfection of RARbeta expression vector into MKN-45 cells resulted in the RARbeta concentration dependent repression of AP-1 activity induced by 12-o-tetradecanoylphorbol-13-acetate (TPA), regardless of the presence of ATRA. When the c-jun and c-fos expression vectors were cotransfected with the RARbeta expression vector into MKN-45 cells, AP-1 activity was also obviously repressed. The inhibitory effect, again, was RARbeta-concentration-dependent. The stable transfection of the RARbeta gene into MKN-45 cells led to cell growth inhibition and colony formation inhibition by ATRA. Furthermore, Cotransfection of both RARbeta/DNA binding domain (DBD) and reporter gene could not alter AP-1 activity, even in the presence of ATRA.However, when the cotransfection was substituted with the RARbeta/ligand binding domain (LBD), the inhibition was significantly enhanced by ATRA.


CONCLUSIONS
RARbeta might be required for anti-AP-1 activity, and contribute to growth inhibition of gastric cancer cells by ATRA.
Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, the School of Life Sciences, Xiamen University, China. xgwu@xmu.edu.cn
Qiao
Q
Wu
Mingqing
M
Zhang
Su
S
Liu
Yuqiang
Y
Chen
Wenjin
W
Su
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D006801:Humans; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000502:physiology*; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000473:pathology; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D018168:Receptors, Retinoic Acid; D018808:Transcription Factor AP-1; C082925:retinoic acid receptor beta; D014212:Tretinoin; D004247:DNA