Flavanones structure-related inhibition on TPA-induced tumor promotion through suppression of extracellular signal-regulated protein kinases: involvement of prostaglandin E2 in anti-promotive process.
Biological functions of flavanones have been studied extensively, however, the structure-related activities of flavanones on 12-o-tetradecanoylphorbol 13-acetate (TPA)-induced promotive effects are still unclear. In this study, flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone showed the most significant dose-dependent inhibition on TPA-induced proliferative effects among eight tested flavanones in NIH3T3 cells. TPA-induced mitogen activated protein kinases (MAPK) phosphorylation, ornithine decarboxylase (ODC), c-Jun, and cyclooxygenase 2 (COX-2) protein expressions in a time-dependent manner, and the maximal inductive time point is at 1 h for MAPK phosphorylation and 6 h for others. Flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone showed the dose-dependent inhibition on TPA-stimulated MAPK phosphorylation, COX-2, ODC, c-Jun protein expressions. Induction of, prostaglandin E(2) (PGE(2)) production was detected in TPA-treated NIH3T3 cells, and flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone inhibited significantly PGE(2) production induced by TPA. Addition of PGE(2) reverses the inhibitory activities of flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone on TPA-induced proliferation. And, PD98059, a specific inhibitor of ERKs, inhibited TPA-induced MAPK phosphorylation, accompanied by decreasing COX-2, c-Jun, and ODC protein expression, and showed dose-dependent inhibition on TPA-induced proliferation in cells. These results demonstrated that PGE(2) is an important mediator in TPA-induced proliferation, and MAPK phosphorylation was located at the upstream of COX-2, c-Jun, and ODC gene expressions in TPA-induced responses. Furthermore, flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone (100 microM) suppressed TPA-induced colony formation associated with blocking MAPK phosphorylation, ODC, c-Jun, and COX-2 proteins expression. And, 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay showed that flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone did not perform potent anti-radical activities among these eight tested compounds. In conclusion, this study provided molecular evidences to demonstrate that flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone were potent inhibitors on TPA-induced responses without notable cytotoxicity through suppression of PGE(2) production; and anti-radical activity of flavanones was not correlated with preventing the occurrence of tumor promotion. We proposed that blocking TPA-induced intracellular signaling responses might be involved in the anti-promotive mechanism of flavanones.
Ko
Ching-Huai
CH
Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, Taipei Medical University, Taipei, Taiwan.
Shen
Shing-Chuan
SC
Lin
Hui-Yi
HY
Hou
Wen-Chi
WC
Lee
Woan-Ruoh
WR
Yang
Ling-Ling
LL
Chen
Yen-Chou
YC
D016475:3T3 Cells; D000818:Animals; D001713:Biphenyl Compounds; D002273:Carcinogens / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010851:Picrates / Q000037:antagonists & inhibitors; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism
D001713:Biphenyl Compounds; D002273:Carcinogens; D005419:Flavonoids; D016166:Free Radical Scavengers; D007527:Isoenzymes; D010851:Picrates; C004931:1,1-diphenyl-2-picrylhydrazyl; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D009955:Ornithine Decarboxylase; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine