 many environmental chemicals and pesticides have been found to be estrogenic and have been shown to stimulate the growth of estrogen receptor - positive ( er - positive ) human breast cancer cells . since it is difficult to avoid human exposure to environmental estrogens , a potentially important area of research is the development of dietary strategies to prevent the stimulated growth of breast tumors by environmental estrogens . in this context , the inhibitory action of curcumin and a combination of curcumin and isoflavonoids were studied in er - positive human breast cancer cells ( mcf-7 and t47d ) and er - negative mda - mb-231 cells induced by the pesticide o , p'-ddt and the environmental pollutants 4-nonylphenol and 4-octylphenol . 
 the median inhibitory concentration ( ic50 ) for curcumin in t47d cells was 10 microm when measured at either a 48-hr or a 6-day incubation time . 
 the ic50 value for curcumin was within the 8 - 10 microm range for inhibiting the growth of t47d cells induced by a 10- microm concentration each of 4-nonylphenol , 4-octylphenol , and o , p'-ddt . 
 the ic50 for curcumin in mcf-7 cells induced by 10 microm of either o , p'-ddt , 4-octylphenol , or 4-nonylphenol were 9 , 39 , and > 50 microm , respectively . 
 a combination of curcumin and isoflavonoids was able to inhibit the induced growth of er - positive cells up to 95% . for mda - mb-231 cells , 
 the ic50 for curcumin was 17 microm , which was reduced to 11 microm in the presence of 25 microm genistein . 
 curcumin and genistein induce drastic changes in the morphological shape of both er - positive and er - negative cells . 
 data presented here indicate that a mixture of curcumin and isoflavonoids is the most potent inhibitor against the growth of human breast tumor cells . 
 these data suggest that combinations of natural plant compounds may have preventive and therapeutic applications against the growth of breast tumors induced by environmental estrogens.imagesfigure 1figure 2figure 3figure 4figure 5figure 6 
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