Cruciferous Vegetables & Lung Cancer

1. Cruciferous Vegetables & Lung Cancer Sharon Lo, Courtney Wheeler, Taylor Seesholtz, & Stephanie Anderson

2. History of Cruciferous Vegetables • The use of cruciferous vegetables began around 7,000 years ago in China & spread throughout Europe during the Middles Ages • The oldest writings indicate they were used for medical purposes • They later gained culinary importance worldwide Hanelt P. Lesser Known or Forgotten Cruciferous Vegetables and Their History. Acta Hort. 1998; 459: 39-45.

3. Cruciferous Vegetables • Brassica family of vegetables including: • Broccoli • Cabbage • Cauliflower • Bok choy • They contain many beneficial compounds, but the plant secondary metabolites, which give them their pungent flavor, are particularly implicated in preventing carcinogenesis.

4. Cruciferous Vegetables Continued • Cruciferous vegetables are high in glucosinolates, which are precursors to isothiocyanates (ITC). • ITC have been implicated for their chemo- preventive effect in mouse models and in epidemiological studies. the glucosinolate molecule

5. Mechanisms • ITC have been shown to reduce lung cancer by inhibiting lung carcinogenesis and enhancing the detoxification of activated carcinogens via glutathione S-transferase (GST) • Glutathione S-transferase M1 & T1 (GSTM1 & GSTT1) combine with ITC, which leads to a more rapid elimination

6. Phase I & Phase II Metabolism • Biotransformation of drugs, chemicals, and endogenous substances in the liver and epithelia need to be cleared from the body. Phase I- Induce, hydroxylation, oxidation, and reduction of foreign substances creating reactive oxygen species. Phase II-Conjugation of metabolite with an enzyme, such as glutathione s-transferases Conaway, C. Current Drug Metabolism. 2002 (3) 233-255.

7. Study 1- Isothiocyanates, GST Polymorphisms, and Lung Cancer Risk Objective: Examine the interaction between total urinary ITC levels and lung cancer risk, in relation to glutathione S-transferases M1 and T1. Methods: A prospective cohort study of 18,244 men in Shanghai, China • incident cases lung cancer (n=232) • matched control (n=710) Design: -Collection of total urinary isothiocyanate levels before diagnosis -Followed from 1986 to 1997 -Homozygous deletion of GSTM1 GSTT1 genes determined by polymerase chain reaction (PCR). London, S. et al. The Lancet. 2000; 356: 724-29.

8. Study 1 - Results

9. Study 1 - Conclusions Conclusions: Participants with detectable amounts of ITC had a decreased risk of developing lung cancer. • Results were heightened when there was a deletion of one or both of the GSTM1 and GSTT1 genes • Deletion of one or both of the genes and no detectible ITC in the urine had a greater risk of developing lung cancer • Lack of dose response in ITC concentration Critique: The study was unable to estimate ITC intake based on a FFQ, so they were limited to only assessing ITC metabolism through the GST pathway. The study also is limited to only having male participants. Grade: B+

10. Study 2- Urinary isothiocyanate levels and lung cancer risk among non-smoking women Objective: To investigate the relationship between cruciferous vegetable consumption and lung cancer risk in non-smoking women. Methods: A nested case-control prospective investigation within the Shanghai women’s health study. • incident lung cancer cases who never smoked (n=209) • individually matched non-smoking controls (n=787) Design: -Cohort was followed from 1997 to 2000. -Urine samples were collected before diagnosis and tested for total urinary isothiocyanate levels as an indicator for cruciferous vegetable consumption. -GST T1 and M1 polymorphisms were extracted from blood or buccal cells and determined by polymerase chain reaction. Fowke, J. et al. Lung Cancer. 2011 July;73(1);18-24.

11. Study 2 - Results *adjusted for age **adjusted for age, a prior asthma diagnosis, fat intake, soy intake, ETS, education, alcohol intake, WHR, number of births, and gstm1 and gstt1 genotypes. ***ORs reflect association for log transformed ITC

12. Study 2 - Conclusions Conclusions: No association between urinary ITC levels and lung cancer among non-smoking women • Positive association with GSTM1-null genotype • Possible interaction between urinary ITC levels, GSTM1 genotype, and lung cancer risk Critique: Urinary ITC testing provides limited (8-72hrs) time period to estimate exposure to cruciferous phytochemicals. Grade: B+

13. Study 3- Dietary intake of Cruciferous vegetables, Glutathione S-transferase (GST) polymorphisms and lung cancer risk in a Caucasian population Objective: To determine the relationship between cruciferous vegetables intake and lung cancer risk related to genotype. Methods: A hospital-based case control study of lung cancer cases and controls. Cruciferous vegetable intake and genotype determined by FFQ and blood sample, respectively. • lung cancer cases (n=716) • controls (n=939) Design: - Data was collected from Massachusetts General Hospital (1992-2000) - Criteria expanded to include operable and inoperable cases in 1996 - Cruciferous vegetable consumption was divided by tertile Wang, L, et al. Cancer Causes and Control. 2004; 15: 977-985

14. Study 3 - Results

15. Study 3- Conclusion Conclusions: Cruciferous vegetable intake was inversely associated with lung cancer risk in GSTMI genotypes. • No difference in results were seen with different cancer stages • The results were seen most prominently among current smokers Critique: This study considered how genotype may affect the relationship between cruciferous vegetable intake and lung cancer risk, while also looking at smoking status. It used trained interviewers to administer the FFQ, but did not match control characteristics with cases. It included a large sample size and considered changes in dietary pattern. It also thoroughly examined potential error and bias. Grade: C+

16. Overall Level of Evidence After assessing the evidence provided in these three articles, we assigned cruciferous vegetables a grade of II for prevention or complementary treatment of lung cancer. Two prospective studies measured urine ITC levels to determine cruciferous vegetable consumption and analyzed contributing factors such GST genotype, gender, location, and exposure to tobacco smoke. There are inconsistencies among results which contributes to uncertainty attached to the conclusion. The third study showed an inverse relationship between cruciferous vegetable intake and lung cancer risk, but depended solely upon a food frequency questionnaire to assess levels of consumption. Studies were inconsistent in their results and suggest more research is needed to delineate the interaction between glucosinolates and lung cancer risk.

17. Public Health Recommendation There is currently not enough research to say eating cruciferous vegetables will prevent or treat lung cancer. We would still suggest eating broccoli, cabbage, and other such vegetables in your diet. These foods are good for your overall health.

18. References Conaway C.C., Yang Y.M., Chung F.L. Isothiocyanates as cancer chemopreventive agents: their biological activities and metabolism in rodents and humans. Current Drug Metabolism.2002;3:233-255 Fowke J.H., Gao Y., Chow,W., et al. Urinary isothiocyanate levels and lung cancer risk among non-smoking women: a prospective investigation. Lung Cancer. 2011; 73:(1): 18-24. Hanelt P. Lesser Known or Forgotten Cruciferous Vegetables and Their History. Acta Hort. 1998; 459: 39-45 London S.J., Yuan, J.M., Chung, F.L., et al. Isothiocyanates, glutathione S-transferase M1 and T1 polymorphisms, and lung-cancer risk: a prospective study of men in Shanghai, China. Lancet.2000; 356:724-729. Wang L.I., Giovannucci E.L., Hunter D., et al. Dietary intake of Cruciferous vegetables, Glutathione S-transferase (GST) polymorphisms and lung cancer risk in a Caucasian population.. Cancer Causes and Controls. 2004; 15: 977-985.