1. Apigenin induced MCF-7 cell apoptosis-associated reactive oxygen species.
Apigenin is a flavonoid, which has been proved to possess effective anti-cancer bioactivities against variety of cell lines. However, little is known about its effect on the cell-surface and the interaction between cell-surface and the reacting drug. In this study, human breast cancer line (MCF-7) was selected to be as a cell model to investigate the effects of apigenin on cell growth, proliferation, apoptosis, cellular morphology, etc. MTT assay showed that the growth inhibition induced by apigenin was in a dose-dependent manner when treated with different concentrations of apigenin while had little cytotoxic effects on human normal cells (MCF-10A). Fluorescence-based flow cytometry was used to detect cellular apoptosis and ROS production. The results showed that 80 µM apigenin could effectively induce apoptosis and overproduction of ROS in MCF-7 cells. Here, atomic force microscopy (AFM) was utilized to detect the shapes and membrane structures of MCF-7 cells at cellular or subcellular level. The results showed that the control MCF-7 cells presented typical elongated-spindle shapes with abundant pseudopodia, while after treated with apigenin, the cells shrunk and became round, the pseudopodia diminished. Moreover, the images of ultrastructure indicated that the cell membrane was composed of nanoparticles of 49?nm, but with the treated concentrations of apigenin increasing, the sizes of membrane particles significantly increased to 400?nm. These results can improve our understanding of apigenin, which can be potentially developed as a new agent for treatment of cancers.
Bai H, Jin H, Yang F, Zhu H, Cai J. Apigenin induced MCF-7 cell apoptosis-associated reactive oxygen species. Scanning. 2014 Oct 18. doi: 10.1002/sca.21170. [Epub ahead of print] PubMed PMID: 25327419.
2. Induction of caspase-dependent apoptosis by apigenin by inhibiting STAT3 signaling in HER2-overexpressing MDA-MB-453 breast cancer cells.
BACKGROUND: This study aimed to examine the effect of apigenin on proliferation and apoptosis in HER2-overexpressing MDA-MB-453 breast cancer cells.
MATERIALS AND METHODS: The antiproliferative effects of apigenin were examined by proliferation and MTT assays. The effect of apigenin on apoptotic molecules was determined by western blotting. RT-PCR was performed to measure mRNA levels of HIF-1? and VEGF. ELISA assay was performed to measure intracellular VEGF levels. Immunocytochemistry was performed to evaluate nuclear STAT3 level.
RESULTS: Apigenin inhibited the proliferation of MDA-MB-453 cells. Apigenin up-regulated the levels of cleaved caspase-8 and caspase-3, and induced the cleavage of PARP. Apigenin induced extrinsic apoptosis and blocked the activation (phosphorylation) of JAK2 and STAT3. Apigenin inhibited CoCl2-induced VEGF secretion and decreased the nuclear staining of STAT3.
CONCLUSION: Apigenin exerts its antiproliferative activity by inhibiting STAT3 signaling. Apigenin could serve as a useful compound to prevent or treat HER2-overexpressing breast cancer.
Seo HS, Ku JM, Choi HS, Woo JK, Jang BH, Shin YC, Ko SG. Induction of caspase-dependent apoptosis by apigenin by inhibiting STAT3 signaling in HER2-overexpressing MDA-MB-453 breast cancer cells. Anticancer Res. 2014 Jun;34(6):2869-82. PubMed PMID: 24922650.
3. Effects of dietary apigenin on tumor latency, incidence and multiplicity in a medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced breast cancer model.
Medroxyprogesterone acetate (MPA) is a synthetic progestin commonly administered to postmenopausal women for hormone replacement therapy and has been associated with increased risk of breast cancer. MPA has been shown to accelerate the development of mammary tumors in a 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer animal model. Previously, we have shown that intraperitoneally administered apigenin effectively treated and prevented the progression of MPA-accelerated breast cancer in DMBA-induced and xenograft mammary cancer models. Here we used the DMBA model to examine the chemopreventive effect of dietary apigenin against MPA-accelerated tumors with 3 different levels of apigenin (0.02%, 0.1%, and 0.5% w/w) incorporated into a phytoestrogen-free diet. Results showed that 0.1% dietary apigenin reduced MPA-dependent tumor incidence; however, the same dietary level increased tumor multiplicity in animals that developed tumors. Neither 0.02% nor 0.5% dietary apigenin reduced MPA-dependent tumor incidence or latency, and tumor multiplicity increased significantly in response to 0.5% apigenin. These results contrast with previous chemopreventive effects observed when apigenin was administered intraperitoneally, suggesting that route of administration may influence its action. Consequently, until further research clarifies the effect of dietary apigenin on progestin-accelerated mammary tumors, caution should be exercised when considering the flavonoid as a dietary supplement for preventing hormone-dependent breast cancer.
Mafuvadze B, Cook M, Xu Z, Besch-Williford CL, Hyder SM. Effects of dietary apigenin on tumor latency, incidence and multiplicity in a medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced breast cancer model. Nutr Cancer. 2013;65(8):1184-91. doi: 10.1080/01635581.2013.833637. Epub 2013 Oct 15. PubMed PMID: 24127693.
4. Autophagy inhibition enhances apigenin-induced apoptosis in human breast cancer cells.
Apigenin (4',5,7-trihydroxyflavone) is a member of the flavone subclass of flavonoids present in fruits and vegetables. The involvement of autophagy in the apigenin-induced apoptotic death of human breast cancer cells was investigated. Cell proliferation and viability were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and clonogenic assays. Flow cytometry, fluorescent staining and Western blot analysis were employed to detect apoptosis and autophagy, and the role of autophagy was assessed using autophagy inhibitors. Apigenin dose- and time-dependently repressed the proliferation and clonogenic survival of the human breast cancer T47D and MDA-MB-231 cell lines. The death of T47D and MDA-MB-231 cells was due to apoptosis associated with increased levels of Caspase3, PARP cleavage and Bax/Bcl-2 ratios. The results from flow cytometry and fluorescent staining also verified the occurrence of apoptosis. In addition, the apigenin-treated cells exhibited autophagy, as characterized by the appearance of autophagosomes under fluorescence microscopy and the accumulation of acidic vesicular organelles (AVOs) by flow cytometry. Furthermore, the results of the Western blot analysis revealed that the level of LC3-II, the processed form of LC3-I, was increased. Treatment with the autophagy inhibitor, 3-methyladenine (3-MA), significantly enhanced the apoptosis induced by apigenin, which was accompanied by an increase in the level of PARP cleavage. Similar results were also confirmed by flow cytometry and fluorescence microscopy. These results indicate that apigenin has apoptosis- and autophagy-inducing effects in breast cancer cells. Autophagy plays a cyto-protective role in apigenin-induced apoptosis, and the combination of apigenin and an autophagy inhibitor may be a promising strategy for breast cancer control.
Cao X, Liu B, Cao W, Zhang W, Zhang F, Zhao H, Meng R, Zhang L, Niu R, Hao X, Zhang B. Autophagy inhibition enhances apigenin-induced apoptosis in human breast cancer cells. Chin J Cancer Res. 2013 Apr;25(2):212-22. doi:10.3978/j.issn.1000-9604.2013.04.01. PubMed PMID: 23592903; PubMed
5. Apigenin induces apoptosis and blocks growth of medroxyprogesterone acetate-dependent BT-474 xenograft tumors.
Recent clinical and epidemiological evidence shows that hormone replacement therapy (HRT) containing both estrogen and progestin increases the risk of primary and metastatic breast cancer in post-menopausal women while HRT containing only estrogen does not. We and others previously showed that progestins promote the growth of human breast cancer cells in vitro and in vivo. In this study, we sought to determine whether apigenin, a low molecular weight anti-carcinogenic flavonoid, inhibits the growth of aggressive Her2/neu-positive BT-474 xenograft tumors in nude mice exposed to medroxyprogesterone acetate (MPA), the most commonly used progestin in the USA. Our data clearly show that apigenin (50 mg/kg) inhibits progression and development of these xenograft tumors by inducing apoptosis, inhibiting cell proliferation, and reducing expression of Her2/neu. Moreover, apigenin reduced levels of vascular endothelial growth factor (VEGF) without altering blood vessel density, indicating that continued expression of VEGF may be required to promote tumor cell survival and maintain blood flow. While previous studies showed that MPA induces receptor activator of nuclear factor kappa-B ligand (RANKL) expression in rodent mammary gland, MPA reduced levels of RANKL in human tumor xenografts. RANKL levels remained suppressed in the presence of apigenin. Exposure of BT-474 cells to MPA in vitro also resulted in lower levels of RANKL; an effect that was independent of progesterone receptors since it occurred both in the presence and absence of the antiprogestin RU-486. In contrast to our in vivo observations, apigenin protected against MPA-dependent RANKL loss in vitro, suggesting that MPA and apigenin modulate RANKL levels differently in breast cancer cells in vivo and in vitro. These preclinical findings suggest that apigenin has potential as an agent for the treatment of progestin-dependent breast disease.
Mafuvadze B, Liang Y, Besch-Williford C, Zhang X, Hyder SM. Apigenin induces apoptosis and blocks growth of medroxyprogesterone acetate-dependent BT-474 xenograft tumors. Horm Cancer. 2012 Aug;3(4):160-71. doi: 10.1007/s12672-012-0114-x. Epub 2012 May 9. PubMed PMID: 22569706.
6. Apigenin induces apoptosis via extrinsic pathway, inducing p53 and inhibiting STAT3 and NF?B signaling in HER2-overexpressing breast cancer cells.
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 I?B? in the cytosol, and abrogated the nuclear translocation of p65 within the nucleus suggesting that it blocks the activation of NF?B 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.
Seo HS, Choi HS, Kim SR, Choi YK, Woo SM, Shin I, Woo JK, Park SY, Shin YC, Ko SG. Apigenin induces apoptosis via extrinsic pathway, inducing p53 and inhibiting STAT3 and NF?B signaling in HER2-overexpressing breast cancer cells. Mol Cell Biochem. 2012 Jul;366(1-2):319-34. doi: 10.1007/s11010-012-1310-2.
7. Apigenin prevents development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats.
The use of progestins as a component of hormone replacement therapy has been linked to an increase in breast cancer risk in postmenopausal women. We have previously shown that medroxyprogesterone acetate (MPA), a commonly administered synthetic progestin, increases production of the potent angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells, leading to the development of new blood vessels and tumor growth. We sought to identify nontoxic chemicals that would inhibit progestin-induced tumorigenesis. We used a recently developed progestin-dependent mammary cancer model in which tumors are induced in Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene (DMBA) treatment. The flavonoid apigenin, which we previously found to inhibit progestin-dependent VEGF synthesis in human breast cancer cells in vitro, significantly delayed the development of, and decreased the incidence and multiplicity of, MPA-accelerated DMBA-induced mammary tumors in this animal model. Whereas apigenin decreased the occurrence of such tumors, it did not block MPA-induced intraductal and lobular epithelial cell hyperplasia in the mammary tissue. Apigenin blocked MPA-dependent increases in VEGF, and suppressed VEGF receptor-2 (VEGFR-2) but not VEGFR-1 in regions of hyperplasia. No differences were observed in estrogen or progesterone receptor (ER/PR) levels, or the number of estrogen receptor-positive cells, within the mammary gland of MPA-treated animals administered apigenin, MPA-treated animals, and placebo treated animals. However, the number of progesterone receptor-positive cells was reduced in animals treated with MPA or MPA and apigenin compared with those treated with placebo. These findings suggest that apigenin has important chemopreventive properties for those breast cancers that develop in response to progestins.
Mafuvadze B, Benakanakere I, López Pérez FR, Besch-Williford C, Ellersieck MR, Hyder SM. Apigenin prevents development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats. Cancer Prev Res (Phila). 2011 Aug;4(8):1316-24. doi: 10.1158/1940-6207.CAPR-10-0382.
8. The dietary flavonoid apigenin blocks phorbol 12-myristate 13-acetate-induced COX-2 transcriptional activity in breast cell lines.
Cyclooxygenase (COX)-2 is the inducible isozyme catalyzing the conversion of arachidonic acid to prostanoids. Its expression has been linked to the process of carcinogenesis, including tumorigenesis of the breast. Apigenin (APG) is a flavone commonly found in fruit and vegetables, and is shown to be a potential modulator in inflammatory diseases. This study examined the potential suppressive effect of the flavone on phorbol ester-induced COX-2 expression in the breast cell lines MCF-10A and MCF-7. Real-time PCR and/or Western blotting indicated that APG in micromolar range significantly inhibited phorbol 12-myristate 13-acetate (PMA)-induced COX-2 expression in these breast cells. APG treatment reduced the amount of phospho-mitogen-activated protein kinase (MAPK) ERK-1/2, but it did not alter the activity of PKC. Activated ERKs might trigger the transactivation of AP-1 or CRE, which can be located at COX-2 promoter region (-72/-53). Reporter gene assay as well as electrophoretic mobility shift assays (EMSA) illustrated that APG inhibited transcription factor binding at this region in a dose-dependent manner. This study showed that APG down-regulated PMA-induced COX-2 expression in breast cells without affecting PKC activity. These findings could provide a scientific basis for developing APG nutraceutical against breast carcinogenesis.
Yi Lau GT, Leung LK. The dietary flavonoid apigenin blocks phorbol 12-myristate 13-acetate-induced COX-2 transcriptional activity in breast cell lines. Food Chem Toxicol. 2010 Oct;48(10):3022-7. doi: 10.1016/j.fct.2010.07.046. Epub 2010 Aug 4. PubMed PMID: 20691240.
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