Tea, Genes and Their Interactions on Breast Cancer

Institution: University of Southern California
Investigator(s): Anna  Wu , Ph.D. -
Award Cycle: 2004 (Cycle 10) Grant #: 10PB-0098 Award: $1,610,872
Award Type: Request for Applications
Research Priorities
Prevention & Risk Reduction>Other searches for the causes



Initial Award Abstract (2004)
Through the funding support from CBCRP, we have conducted a large case-control study of breast cancer among Asian-Americans in Los Angeles County. We have, as others, found that risk of breast cancer is reduced in association with soy intake, particularly with childhood intake. There is also some modest risk reduction among women who only started eating soy as adults but this finding is based on limited numbers. We provided the first piece of evidence from epidemiological studies that tea intake, particularly, green tea, may protect against breast cancer. In addition, the tea-breast cancer association may depend on your genetic background. Because the role of tea was not a specific hypothesis in our original study, our questions were relatively crude and limited to current intake pattern. This proposed study has been designed to address some of the gaps in knowledge regarding the role of tea and soy.

The questions we wish to explore include: Does the type of tea matter (green tea vs black tea)? If green tea can be confirmed to be more beneficial than black tea, can this be explained by the differing effects of green tea and black tea on circulating estrogens as suggested by our preliminary findings? How much tea drinking is needed? Is the protection found only among current tea drinkers? Is the protection found primarily among women who possess a certain genetic background, namely, those who are less efficient in eliminating tea products so that they derive the most benefit from drinking tea? Do you get the most benefit if you eat both soy and drink tea? In addition, what is the benefit of eating soy foods as an adult if you are a non-soy consumer during childhood.

We are proposing to continue this case-control study by recruiting an additional 750 breast cancer patients and 750 control subjects. This new dataset will allow us to confirm our tea finding by obtaining more detailed information on lifetime tea drinking habits. The questionnaire data and DNA materials collected in this proposed study will be combined with the large database of information (from over 1200 cases and 1100 controls) in the current study. The combined database will be used to investigate the role of genes involved in the metabolism of tea and soy. This information will give us some clues regarding who may derive the most benefit from these foods. Finally, we plan to use serum samples from postmenopausal control women to confirm a preliminary finding that circulating estrogen levels may be increased in association with black tea but decreased with green tea intake.

This population of Asian-American women in LA County is uniquely suited to address these questions. From our previous study, we have identified tea and soy as two components of the Asian diet which may have contributed, in part, to the traditionally lower risk of breast cancer. However, these results need confirmation with larger sample sizes and with improved assessment of lifetime tea intake. If the beneficial effects of soy and/or tea can be confirmed, these dietary agents can be easily incorporated in the diets across all racial/ethnic populations.


Final Report (2008)
This population-based, case-control study of breast cancer in Asian-American women included completed interviews with 937 women with breast cancer (437 Chinese, 174 Japanese, 304 Filipino, 22 other Asians) and 774 control women (355 Chinese, 160 Japanese, 191 Filipino, 68 other Asians) without breast cancer. Breast cancer cases were diagnosed with histologically confirmed primary incident breast cancer, at ages 75 or younger, and were residents of Los Angeles County at the time of diagnosis. The primary objective of this investigation was to further study the tea-breast cancer and soy-breast cancer associations. Specifically, we determined if risk of breast cancer varied with the dose, duration, and other parameters of green tea and black tea drinking. We also determined if breast cancer risk was reduced among women who were exposed to soy intake as adults but not as adolescents. Our secondary objectives were to determine the potential modifying effects of select genes, including metabolic genes (COMT, SULT1A1, UGT1A1) and oxidative stress-related genes (MnSOD, OGG1-8) on the tea-breast cancer and soy-breast cancer associations. In addition, we investigated the relationship between blood levels of sex hormones, sex hormone binding globulin (SHBG) and intake of tea and soy among postmenopausal control women who were not current hormone users at the time of blood donation.

In our analysis to date, we found a significant trend of decreasing risk with increasing amount of green tea intake (p<0.001); there was about a 50% risk reduction among daily green tea consumers. Current green tea drinking appeared to be more important; we did not find any significant association between duration of green tea drinking and risk of breast cancer. Breast cancer risk was unrelated to amount and duration of black tea drinking. Breast cancer risk was significantly inversely associated with soy food intake during adolescence and adult life. Compared with women who were low consumers during both time periods, significant risk reductions were found among women who were high soy consumers during adult life only (RR=0.71, p<0.05). Intake of green tea and soy had significant independent effects on breast cancer risk when lifetime intake of both food groups were considered simultaneously.

Our results showed that the soy-breast cancer association and the green tea-breast cancer associations were not significantly modified by the single SNPs (see above) we investigated. We also did not find any significant relationships between plasma levels of SHBG and sex hormones and intake of soy and green tea among postmenopausal control women.
Body size, hormone therapy and risk of breast cancer in Asian-American women.
Periodical:International Journal of Cancer
Index Medicus: Int J Cancer
Authors: Wu AH, Yu MC, Tseng CC, Pike MC
Yr: 2006 Vol: 120 Nbr: Abs: Pg:844-852
Estimated Asian adult soy protein and isoflavone intakes.
Periodical:Nutrition and Cancer
Index Medicus: Nutr Cancer.
Authors: Messina M, Nagata C, Wu AH.
Yr: 2006 Vol: 56 Nbr: 2 Abs: Pg:128-135
Diabetes and risk of breast cancer in Asian-American women.
Periodical:Carcinogenesis
Index Medicus: Carcinogenesis
Authors: Wu AH, Yu MC, Tseng CC, Stanczyk FZ, Pike MC.
Yr: 2007 Vol: 28 Nbr: 7 Abs: Pg:1561-1566
Tamoxifen, Soy, and Lifestyle Factors in Asian American Women With Breast Cancer.
Periodical:Journal of Clinical Oncology
Index Medicus: J Clin Oncol
Authors: Wu AH, Pike MC, Williams LD, Spicer D, Tseng CC, Churchwell MI, Doerge DR.
Yr: 2007 Vol: Nbr: Abs: Pg:
Comprehensive association testing of common genetic variation in DNA repair pathway genes in relationship with breast cancer risk in multiple populations.
Periodical:Human Molecular Genetics
Index Medicus: Hum Mol Genet
Authors: Haiman CA et al, Wu AH, Stram DO, Henderson BE.
Yr: 2008 Vol: 17 Nbr: 6 Abs: Pg:825-34
A promoter polymorphism in the CASP8 gene is not associated with cancer risk.
Periodical:Nature Genetics
Index Medicus: Nat Genet
Authors: Haiman CA, Garcia RR, Kolonel LN, Henderson BE, Wu AH, Le Marchand L
Yr: 2008 Vol: 40 Nbr: 3 Abs: Pg:259-260
Dietary patterns and breast cancer risk in Asian American women.
Periodical:American Journal of Clinical Nutrition
Index Medicus: Am J Clin Nutrition
Authors: Wu AH, Yu MC, Tseng CC, Stanczyk FZ, Pike MC
Yr: 2009 Vol: 89 Nbr: 4 Abs: Pg:1145-54