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.
Wu
Qiao
Q
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
Zhang
Mingqing
M
Liu
Su
S
Chen
Yuqiang
Y
Su
Wenjin
W
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