title: Apigenin induces apoptosis via extrinsic pathway, inducing p53 and inhibiting STAT3 and NFκB signaling in HER2-overexpressing breast cancer cells.
abstract: Phytoestrogens are known to prevent tumor induction. But their molecular mechanisms of action are still unknown. This study aimed to examine the effect of apigenin on proliferation and apoptosis in HER2-expressing breast cancer cells. In our experiments, apigenin inhibited the proliferation of MCF-7 vec and MCF-7 HER2 cells. This growth inhibition was accompanied with an increase of sub G(0)/G(1) apoptotic fractions. Overexpression of HER2 did not confer resistance to apigenin in MCF-7 cells. Apigenin-induced extrinsic apoptosis pathway up-regulating the levels of cleaved caspase-8, and inducing the cleavage of poly (ADP-ribose) polymerase, whereas apigenin did not induce apoptosis via intrinsic mitochondrial apoptosis pathway since this compound did not decrease mitochondrial membrane potential maintaining red fluorescence and did not affect the levels of B-cell lymphoma 2 (BCL2) and Bcl-2-associated X protein. Moreover, apigenin reduced the tyrosine phosphorylation of HER2 (phospho-HER2 level) in MCF-7 HER2 cells, and up-regulated the levels of p53, phospho-p53 and p21 in MCF-7 vec and MCF-7 HER2 cells. This suggests that apigenin induces apoptosis through p53-dependent pathway. Apigenin also reduced the expression of phospho-JAK1 and phospho-STAT3 and decreased STAT3-dependent luciferase reporter gene activity in MCF-7 vec and MCF-7 HER2 cells. Apigenin decreased the phosphorylation level of IκBα in the cytosol, and abrogated the nuclear translocation of p65 within the nucleus suggesting that it blocks the activation of NFκB signaling pathway in MCF-7 vec and MCF-7 HER2 cells. Our study indicates that apigenin could be a potential useful compound to prevent or treat HER2-overexpressing breast cancer.
authors.affiliation: Laboratory of Clinical Biology and Pharmacogenomics and Center for Clinical Research and Genomics, Institute of Oriental Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
authors.forename: Hye-Sook
authors.initials: HS
authors.lastname: Seo
authors.forename: Han-Seok
authors.initials: HS
authors.lastname: Choi
authors.forename: Soon-Re
authors.initials: SR
authors.lastname: Kim
authors.forename: Youn Kyung
authors.initials: YK
authors.lastname: Choi
authors.forename: Sang-Mi
authors.initials: SM
authors.lastname: Woo
authors.forename: Incheol
authors.initials: I
authors.lastname: Shin
authors.forename: Jong-Kyu
authors.initials: JK
authors.lastname: Woo
authors.forename: Sang-Yoon
authors.initials: SY
authors.lastname: Park
authors.forename: Yong Cheol
authors.initials: YC
authors.lastname: Shin
authors.forename: Seong-Gyu
authors.initials: SG
authors.lastname: Ko
authors.forename: Seong-Kyu
authors.initials: SK
authors.lastname: Ko
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D047310:Apigenin / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D016328:NF-kappa B / Q000378:metabolism; D048789:Phytoestrogens / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D047310:Apigenin; D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D048789:Phytoestrogens; D018719:Erb-b2 Receptor Tyrosine Kinases; D050796:STAT3 Transcription Factor; D016159:Tumor Suppressor Protein p53; C494086:STAT3 protein, human; C495901:TP53 protein, human; C508053:ERBB2 protein, human