Person:

Ogino, Shuji

Background: Menopausal hormone therapy (MHT) use has been consistently associated with a decreased risk of colorectal cancer (CRC) in women. Our aim was to use a genome-wide gene–environment interaction analysis to identify genetic modifiers of CRC risk associated with use of MHT. Methods: We included 10 835 postmenopausal women (5419 cases and 5416 controls) from 10 studies. We evaluated use of any MHT, oestrogen-only (E-only) and combined oestrogen–progestogen (E+P) hormone preparations. To test for multiplicative interactions, we applied the empirical Bayes (EB) test as well as the Wald test in conventional case–control logistic regression as primary tests. The Cocktail test was used as secondary test. Results: The EB test identified a significant interaction between rs964293 at 20q13.2/CYP24A1 and E+P (interaction OR (95% CIs)=0.61 (0.52–0.72), P=4.8 × 10−9). The secondary analysis also identified this interaction (Cocktail test OR=0.64 (0.52–0.78), P=1.2 × 10−5 (alpha threshold=3.1 × 10−4). The ORs for association between E+P and CRC risk by rs964293 genotype were as follows: C/C, 0.96 (0.61–1.50); A/C, 0.61 (0.39–0.95) and A/A, 0.40 (0.22–0.73), respectively. Conclusions: Our results indicate that rs964293 modifies the association between E+P and CRC risk. The variant is located near CYP24A1, which encodes an enzyme involved in vitamin D metabolism. This novel finding offers additional insight into downstream pathways of CRC etiopathogenesis.

Background: Flavonoids inhibit the growth of colon cancer cells in vitro. In a secondary analysis of a randomized controlled trial, the Polyp Prevention Trial, a higher intake of one subclass, flavonols, was statistically significantly associated with a reduced risk of recurrent advanced adenoma. Most previous prospective studies on colorectal cancer evaluated only a limited number of flavonoid subclasses and intake ranges, yielding inconsistent results. Objective: In this study, we examined whether higher habitual dietary intakes of flavonoid subclasses (flavonols, flavones, flavanones, flavan-3-ols, and anthocyanins) were associated with a lower risk of colorectal cancer. Design: Using data from validated food-frequency questionnaires administered every 4 y and an updated flavonoid food composition database, we calculated flavonoid intakes for 42,478 male participants from the Health Professionals Follow-Up Study and for 76,364 female participants from the Nurses’ Health Study. Results: During up to 26 y of follow-up, 2519 colorectal cancer cases (1061 in men, 1458 in women) were documented. Intakes of flavonoid subclasses were not associated with risk of colorectal cancer in either cohort. Pooled multivariable adjusted RRs (95% CIs) comparing the highest with the lowest quintiles were 1.04 (0.91, 1.18) for flavonols, 1.01 (0.89, 1.15) for flavones, 0.96 (0.84, 1.10) for flavanones, 1.07 (0.95, 1.21) for flavan-3-ols, and 0.98 (0.81, 1.19) for anthocyanins (all P values for heterogeneity by sex >0.19). In subsite analyses, flavonoid intake was also not associated with colon or rectal cancer risk. Conclusion: Our findings do not support the hypothesis that a higher habitual intake of any flavonoid subclass decreases the risk of colorectal cancer.