Induction of apoptosis by TPA and VP-16 is through translocation of TR3.
OBJECTIVE
To investigate the role of TR3 in induction of apoptosis in gastric cancer cells.


METHODS
Human gastric cancer cell line, MGC80-3, was used. Expression of TR3 mRNA and its protein was detected by Northern blot and Western blot. Localization of TR3 protein was showed by immunofluorescence analysis under laser-scanning confocal microscope. Apoptotic morphology was observed by DAPI fluorescence staining, and apoptotic index was counted among 1000 cells randomly. Stable transfection assay was carried out by Lipofectamine.


RESULTS
Treatment of MGC80-3 cells with TPA and VP-16 resulted in apoptosis, accompanied by the repression of Bcl-2 protein in a time-dependent manner. At the same time, TPA and VP-16 also up-regulated expression level of TR3 mRNA in MGC80-3 cells that expressed TR3 mRNA. When antisense-TR3 expression vector was transfected into the cells, expression of TR3 protein was repressed. In this case, TPA and VP-16 did not induce apoptosis. In addition, TPA and VP-16-induced apoptosis involved in translocation of TR3. In MGC80-3 cells, TR3 localized concentrative in nucleus, after treatment of cells with TPA and VP-16, TR3 translocated from nucleus to cytosol obviously. However, when this nuclear translocation was blocked by LMB, apoptosis was not occurred in MGC80-3 cells even in the presence of TPA and VP-16.


CONCLUSIONS
Induction of apoptosis by TPA and VP-16 is through induction of TR3 expression and translocation of TR3 from nucleus to cytosol, which may be a novel signal pathway for TR3, and represent the new biological function of TR3 to exert its effect on apoptosis in gastric cancer cells.
Liu
Su
S
Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005,Fujian Province,China.
Wu
Qiao
Q
Ye
Xiao-Feng
XF
Cai
Jian-Huai
JH
Huang
Zhi-Wei
ZW
Su
Wen-Jin
WJ
D021581:Active Transport, Cell Nucleus; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005047:Etoposide / Q000494:pharmacology; D015870:Gene Expression; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D005047:Etoposide; D013755:Tetradecanoylphorbol Acetate