apigenin inhibits angiogenesis induced by cancer cells and can be used to inhibit tumor angiogenesis and tumor growth , and to inhibit angiogenic inducers such as vascular endothelial growth factor and hypoxia - inducible factor 1 . apigenin ( 4 ′, 5 , 7 ,- trihydroxyflavone ) is a common dietary flavonoid . it has low toxicity , is non - mutagenic , and is widely distributed in many fruits and vegetables , including parsley , onions , oranges , tea , chamomile , wheat sprouts , and in some seasonings ( 1 ). apigenin is used as a health food supplement and recently has been shown to possess anti - tumor properties ( 2 - 5 ). our data indicate apigenin &# 39 ; s potential in the chemotherapeutic and chemopreventive treatment of cancers . human cancers have become the leading cause of death in america for people under the age of 85 . the five year survival rate for most human cancers has decreased but the mechanism ( s ) of human cancer still remains unknown ( 6 ). while cisplatin , taxol and other therapeutic reagents are commonly used drugs in treating human cancers , cancer cells have been shown to gradually develop resistance to the therapeutic agents , eventually resulting in the death of the patients . therefore it is very important to find a new reagent to enhance the therapeutic reagents for treating human cancers . hence , apigenin is a promising drug when combined with therapeutic reagents for cancer chemotherapy . although apigenin has been shown to inhibit a few cancer cell lines , including colon , breast , and prostate cancer , its effects on enhancing chemotherapy and the chemotherapeutic effects of other agents when they are combined are unknown . in our research , we used the ovarian cancer cell lines a2780 / cp70 and ovcar - 3 and prostate cancer cells pc - 3 as model systems . we found that apigenin , at physiological concentrations , selectively inhibited cancer cells &# 39 ; proliferation and induced cell apoptosis ( fig1 ). under the same experimental conditions , apigenin had little effects on the human normal fibroblast cells ( fig1 ). apigenin may inhibit ovarian cancer cells &# 39 ; growth via inhibition of the ( phosphoinositide 3 - kinase ) pi3k / akt pathway , induction of p53 , p21 , and bax , and activation of caspase cascades . furthermore , we found that apigenin inhibited in vivo tumor growth of ovarian cancer cells ( fig2 ). we also found that apigenin enhanced the sensitivity of cisplatin - resistant a2780 / cp70 cells to cisplatin treatment ( fig3 ), and the sensitivity of several human cancer cells to taxol , cisplatin , mitomycin c , doxorubicin and other therapeutic reagents . based on the daily dietary consumption of flavonoids , the concentration of apigenin used in this work is nontoxic and physiologically relevant in humans . our results indicate that apigenin possesses the potential to inhibit cancer cell proliferation , tumor growth , and angiogenesis ; and suggests a potential application of apigenin as a chemopreventive agent against human ovarian , lung , colon , prostate , and other cancers ; and as chemotherapeutic agent to enhance the effects of other chemotherapeutic agents . we found in this study that apigenin also possess the potential to inhibit tumor angiogenesis . angiogenesis is the formation of new blood vessels . a tumor will not grow without new blood vessel formation because it needs newly - formed blood vessels to transport nutrients and oxygen ( 8 , 9 ). angiogenesis is activated by many factors , among which is the vascular endothelial growth factor ( vegf ) ( 9 ). many cancer cells produce vegf . the vegf produced by cancer cells induces new blood vessel formation . the production of vegf is mainly regulated by hypoxia - inducible factor 1 ( hif - 1 ) ( 10 ). hif - 1 is a transcription factor , composed of hif - 1α and hif - 1β subunits . hif - 1α is unique to hif - 1 and is induced in response to a decrease in cellular o2 concentration and some growth factors . hif - 1 is identical to the aryl hydrocarbon nuclear translocator that forms a heterodimer with an aryl hydrocarbon receptor and is not regulated by cellular oxygen tension or growth factors . hif - 1 is overexpressed in many human cancers ( 11 ), and the levels of its activity in cells correlate with tumorigenicity and angiogenesis ( 12 ). vegf and its upstream target hif - 1 are common targets in all cancer treatments . thus , the combination of apigenin with therapeutic reagents can be applied to all cancer therapy . in reference to fig4 , apigenin greatly enhanced cisplatin - inhibited tumor formation induced by a2780 / cp70 ovarian cancer cells . the results show that 2 . 5 μm cisplatin ( cddp ) just slightly inhibited tumor growth since a2780 / cp70 cells are cddp resistant ( fig4 ). 10 μm apigenin inhibited a2780 / cp70 tumor growth by 40 %. the combination of cddp and apigenin resulted in the inhibition of tumor growth by 70 % ( fig4 b ). the results of blood vessel formation are consistent with those of our tumor assay . cddp alone slightly inhibited the blood vessel formation induced by the cancer cells ( fig4 c ). apigenin inhibited the blood vessel formation ( angiogenesis ) by 35 %. when cddp was combined with apigenin , the inhibition rate of angiogenesis increased to 60 %. taken together , our results suggest that apigenin can sensitize the a2780 / cp70 ovarian cancer cells to cddp , and enhance the effects of drug therapy used to treat human cancer . these data indicate that apigenin is useful in combination with other chemotherapy agents including cddp for the therapeutic treatment of ovarian and other cancers . apigenin inhibited cell proliferation and induced apoptosis in ovarian and prostate cancer cells in culture . the effects of apigenin on prostate cancer cell proliferation were determined using the pc - 3 and du145 cell lines . as shown in fig8 , apigenin alone inhibited both pc - 3 and du145 cell proliferation . the effect of combining apigenin and cisplatin ( a commonly used anti - cancer drug ) on cancer cells was determined . the cisplatin - resistant ovarian cancer cell line a2780 / cp70 and the prostate cancer cell line pc - 3 served as a model . the concentration needed to inhibit 50 % of a2780 / cp70 cell proliferation was approximately 20 μm of cisplatin ( ic50 ). the addition of 10 μm of apigenin decreased ic50 to 5 μm ( 4 - fold reduction ). similar results were observed with pc - 3 cells . as shown in fig9 , the addition of apigenin significantly increased the sensitivity of the pc - 3 cells to cisplatin . in the presence of 10 μm of apigenin , only 3 μm of cisplatin resulted in a 50 % inhibition of pc - 3 cell proliferation ( 7 - fold reduction ). these results suggest that the combination of cisplatin with apigenin greatly enhanced the toxic effects of cisplatin on the cancer cells . apoptosis was monitored as another index of apigenin and cisplatin effects on cancer cell sensitivity . we used a2780 / cp70 cells in this experiment . as shown in fig1 , 10 μm of cisplatin resulted in low levels of apoptosis of a2780 / cp70 cells in 24 h . 10 μm of apigenin resulted in 12 % of the cells undergoing apoptosis . a combination of cisplatin and apigenin led to 25 % of the cells undergoing apoptosis ( fig1 ). the effect of combining apigenin and taxol on cancer cell apoptosis was determined . the prostate cancer cell line pc - 3 and the ovarian cancer cell line a2780 / cp70 served as a model . as shown in fig1 a , the addition of 20 μm of apigenin significantly induced cellular apoptosis of pc - 3 cells in the presence of taxol . the ic50 of cell viability decreased from 577 . 19 nm in the presence of taxol alone to 50 . 33 nm with the addition of apigenin . the addition of 20 μm of apigenin also induced the cellular apoptosis rate in a2780 / cp70 cells ( fig1 b ). the ic50 of cell viability decreased from 503 . 44 nm with taxol alone to 225 . 02 nm with the addition of apigenin . these results suggest that the combination of taxol and apigenin greatly increased the rate of cancer cell death and chemotherapeutic effects . apigenin significantly inhibits lung cancer cell proliferation ( fig1 ). apigenin also dramatically suppresses vegf transcriptional activation and hif - 1 protein expression in lung cancer cells ( fig1 , 14 ). consistent with the in vitro data , apigenin has significant effects on tumor growth and tumor angiogenesis in vivo ( fig1 , 16 ). apigenin shows strong inhibitory effects on cell proliferation of several other cancer cells , including prostate and colon cancers ( fig1 ). we have shown that apigenin exhibits anticancer effects on multiple cancer cell types , including ovarian , prostate , colon , and lung cancer , suggesting that apigenin has broad anticancer effects that may be useful for all human cancers . apigenin was shown to increase the sensitivity of prostate , colon , and lung cancer cells to many commonly used chemotherapy reagents , such as doxorubicin , etoposide , mitomycin c , fluorouracil , taxol , and cisplatin ( fig1 , 18 - 22 ). these data suggest that apigenin may synergize with most or all the chemotherapeutic drugs for cancer treatment . importantly , apigenin greatly decreases the doses of many chemotherapy drugs in inhibiting cancer cell growth . apigenin reduces the ic50 ( inhibiting 50 % cell proliferation ) of fluorouracil by 70 % of inhibiting du145 prostate cancer cells ( fig2 a ), and reduces the ic50 of doxorubicin by 2 - fold on pc - 3 prostate cancer cells ( fig2 b ). apigenin decreases the ic50 of cisplatin by 3 - fold , and mitomycin c by 7 - fold on colo - 205 colon cancer cell ( fig2 a ). the ic50 of cisplatin and doxorubicin for inhibiting h460 lung cancer cells was decreased by 20 - fold by the combination of apigenin treatment with cisplatin and doxorubicin , respectively ( fig2 b ). taken together , our data suggest that apigenin can improve the effectiveness and decrease the doses of conventional chemotherapeutic drugs for cancer treatment , and therefore has great clinical significance for the therapeutic regime for many or all human cancers . it is to be understood that the present invention is not limited to the embodiments described above , but encompasses any and all embodiments within the scope of the following claims . 1 . duthie , g ., crozier , a . ( 2000 ) plant - derived phenolic antioxidants . curr . opin . clin . nutr . metab care 3 , 447 - 451 . 2 . gupta , s ., afaq , f ., mukhtar , h . ( 2001 ) selective growth - inhibitory , cell - cycle deregulatory and apoptotic response of apigenin in normal versus human prostate carcinoma cells . biochem . biophys . res . commun . 287 , 914 - 920 . 3 . wang , w ., heideman , l ., chung , c . s ., pelling , j . c ., koehler , k . j ., birt , d . f . ( 2000 ) cell - cycle arrest at g2 / m and growth inhibition by apigenin in human colon carcinoma cell lines . mol . carcinog . 28 , 102 - 110 . 4 . yin , f ., giuliano , a . e ., law , r . e ., van herle , a . j . ( 2001 ) apigenin inhibits growth and induces g2 / m arrest by modulating cyclin - cdk regulators and erk map kinase activation in breast carcinoma cells . anticancer res . 21 , 413 - 420 . 5 . fotsis , t ., pepper , m . s ., aktas , e ., breit , s ., rasku , s ., adlercreutz , h ., wahala , k ., montesano , r ., schweigerer , l . ( 1997 ) flavonoids , dietary - derived inhibitors of cell proliferation and in vitro angiogenesis . cancer res . 57 , 2916 - 2921 . 6 . perez , r . p ., godwin , a . k ., hamilton , t . c ., and ozols , r . f . 1991 . ovarian cancer biology . semin . oncol . 18 : 186 - 204 . 7 . greenlee , r . t ., hill - harmon , m . b ., murray , t ., and thun , m . 2001 . cancer statistics , 2001 . ca cancer j . clin . 51 : 15 - 36 . 8 . folkman , j . ( 2002 ) role of angiogenesis in tumor growth and metastasis . semin . oncol . 29 , 15 - 18 . 9 . plate , k . h ., breier , g ., weich , h . a ., risau , w . ( 1992 ) vascular endothelial growth factor is a potential tumour angiogenesis factor in human gliomas in vivo . nature 359 , 845 - 848 . 10 . semenza , g . l . ( 2000 ) hypoxia , clonal selection , and the role of hif - 1 in tumor progression . crit rev . biochem . mol . biol . 35 , 71 - 103 . 11 . zhong , h ., de marzo , a . m ., laughner , e ., lim , m ., hilton , d . a ., zagzag , d ., buechler , p ., isaacs , w . b ., semenza , g . l ., simons , j . w . ( 1999 ) overexpression of hypoxia - inducible factor 1alpha in common human cancers and their metastases . cancer res . 59 , 5830 - 5835 . 12 . maxwell , p . h ., dachs , g . u ., gleadle , j . m ., nicholls , l . g ., harris , a . l ., stratford , i . j ., hankinson , o ., pugh , c . w ., ratcliffe , p . j . ( 1997 ) hypoxia - inducible factor - 1 modulates gene expression in solid tumors and influences both angiogenesis and tumor growth . proc . natl . acad . sci . u . s . a 94 , 8104 - 8109 . 13 . conklin k a . ( 2000 ) dietary antioxidants during cancer chemotherapy : impact on chemotherapeutic effectiveness and development of side effects . nutr cancer . 37 , 1 - 18 .
apigenin is a nontoxic compound . the present invention is appropriate for apigenin use in people who have a high risk of getting cancer , and in people who have cancer through chemoprevention and chemotherapy , respectively . we showed that apigenin inhibited cancer cell proliferation , tumor growth and angiogenesis . apigenin selectively inhibited proliferation and induced apoptosis of cancer cells , enhanced the sensitivity of different cancer cells to different therapeutic drugs including cisplatin and taxol . apigenin also inhibits angiogenesis and tumor growth in human cancers , and inhibits angiogenic inducers such as hypoxia - inducible factor 1 and vascular endothelial growth factor . apigenin inhibited expression of hif - 1 and vegf through pi3k , akt , p70s6k1 and hdm2 pathways , which are commonly observed in all kinds of human cancers . thus , our results indicate that apigenin can be applied to various human cancers for chemoprevention , and for chemotherapy when combined with other therapeutic reagents .