Interference effect of epigallocatechin-3-gallate on targets of nuclear factor kappaB signal transduction pathways activated by EB virus encoded latent membrane protein 1.
OBJECTIVE
To elucidate the interference effect of epigallocatechin-3-gallate (EGCG) on targets of nuclear factor kappaB (NF-kappaB) signal transduction pathway activated by EB virus encoded latent membrane protein 1 (LMP1) in nasopharyngeal carcinoma (NPC) cell lines.


METHODS
The survival rates of CNE1 and CNE-LMP1 cell lines after the EGCG treatment were determined by MTT assay. NF-kappaB activation in CNE1 and CNE-LMP1 cells after EGCG treatment was analyzed by promoter luciferase reporter system. And then nuclear translocation of NF-kappaB (p65) after the EGCG treatment was analyzed by immunofluorescence and western blotting. Meanwhile, the changes of IkappaBalpha phosphorylation were observed after the EGCG treatment. EGFR promoter activity was analyzed by promoter luciferase reporter system and EGFR phosphorylation was observed by western blotting after the EGCG treatment.


RESULTS
EGCG inhibited the survival rates of CNE1 and CNE-LMP1 cells and NF-kappaB activation caused by LMP1 in CNE-LMP1 cells. EGCG also suppressed the nuclear translocation of NF-kappaB (p65) and IkappaBalpha phosphorylation. Meanwhile, EGCG inhibited EGFR promoter activity and EGFR phosphorylation.


CONCLUSIONS
EGCG inhibited not only the dose-dependent survival rate of NPC cells, but also the dose-dependent activation of NF-kappaB. This inhibition of LMP1-caused NF-kappaB activation was mediated via the phosphorylative degradation of its inhibitory protein IkappaBalpha, and then EGCG inhibited EGFR activity which was a downstream gene from NF-kappaB. This study suggests that interference effect of EGCG on targets of signal transduction pathway plays an important role in the anticancer function.
Yan
Zhao
Z
Cancer Research Institute, Xiangya School of Medicine, Central South University, 88 Xiangya Road, Changsha 410078, Hunan, PR China. yan68cn@yahoo.com
Yong-Guang
Tao
T
Fei-Jun
Luo
L
Fa-Qing
Tang
T
Min
Tang
T
Ya
Cao
C
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000970:Antineoplastic Agents / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D066246:ErbB Receptors / Q000235:genetics; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009303:Nasopharyngeal Neoplasms / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D051996:Transcription Factor RelA; D014763:Viral Matrix Proteins / Q000502:physiology*
D000970:Antineoplastic Agents; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D051996:Transcription Factor RelA; D014763:Viral Matrix Proteins; D000072000:NF-KappaB Inhibitor alpha; D002392:Catechin; C045651:epigallocatechin gallate; D066246:ErbB Receptors