What changes to your lifestyle could help reduce your cancer risk? According to the National Cancer Institute, lifestyle choices, including poor diet, excess exposure to sunlight, and cigarette smoking, are environmental factors that can increase cancer risk. In the Masonic Cancer Center's Population Sciences research programs, the role of "healthy lifestyle" choices—including diet and exercise—in cancer prevention is being intensely studied through collaborative research work.

Cancer Center member Mindy Kurzer, Ph.D., is professor of nutrition and director of the University of Minnesota Healthy Foods, Healthy Lives Institute. She is studying the effects of dietary factors on levels of cancer biomarkers, which are substances in the blood, tissue, or urine, that are known to be associated with cancer risk. Among her interests: investigating how intake of soy affects prostate cancer biomarker levels.

"Much more work on soy has been done in women, looking at breast cancer, than in men, and very few studies have looked in tissues at meaningful endpoints, such as cancer-related proteins," says Kurzer.

Her group recently looked at the effects of soy intake on prostate cancer biomarkers in a small group of men with a high risk of developing prostate cancer. They found that while soy intake was associated with significantly lower levels of one biomarker for prostate cancer, other biomarkers and reproductive hormones were princiunchanged. She is now using proteomics, which is the study of the structure and function of proteins, to examine that study's samples to determine if soy consumption alters expression of prostate tissue proteins. The application of proteomic technology to dietary studies is incredibly new, says Kurzer.

Kurzer is also studying the effects of exercise on biomarkers for breast cancer risk. The Women in Steady Exercise Research (WISER) study is measuring a number of biomarkers in women who are participating in a vigorous aerobic exercise program. By analyzing both the biomarker data obtained during the study and information collected from study participants on variables such as reproductive history, body weight, and dietary intake, the study will lead to a better understanding of how exercise can reduce breast cancer risk.

New energetics and cancer initiative

Kurzer's WISER study is part of the new University center that is funded by a five-year, $10 million grant awarded to the University of Minnesota from the National Cancer Institute (NCI) under its Transdisciplinary Research on Energetics and Cancer (TREC) initiative. The NCI TREC initiative awarded grants to four research centers nationally in 2005, with the goal of advancing progress toward understanding the relationship between cancer risk and obesity, poor diet, and low levels of physical activity. In addition to WISER, the TREC center funds two other projects led by Cancer Center members, one on the causes of adolescent obesity (Leslie Lytle, Ph.D., project leader) and another on preventing weight gain in families by modifying household environment (Simone French, Ph.D., project leader).

According to Robert Jeffery, Ph.D., professor of epidemiology and community health and principal investigator of the TREC center grant, "the idea of the TREC center is getting diverse groups of researchers with different disciplinary backgrounds together to study obesity and cancer."

Jeffery, who also directs the University's Obesity Prevention Center, notes that the University of Minnesota was an attractive applicant for TREC funding because of the quality and breadth of expertise of University researchers in this specific area of research. Beyond supporting research projects, the NCI funds provide the TREC center with significant support for career development of trainees and junior researchers.

"To be able to work with the next generation of researchers and try to help them refine their skills and develop their careers has been particularly gratifying," says Jeffery.

Tobacco research and cancer prevention strategies

Stephen Hecht, Ph.D., has spent much of his career investigating tobacco use. He studies the molecular mechanisms by which tobacco carcinogens lead to lung cancer, with a keen interest in developing prevention strategies. As far back as the 1980s, Hecht, the Winston R. and Maxine H. Wallin Land Grant Chair in Cancer Prevention and the leader of the Masonic Cancer Center's Carcinogenesis and Chemoprevention Research Program, became interested in how naturally occurring compounds, including those in fruits and vegetables, can reduce the risk of developing tobacco carcinogeninduced lung cancer.

"We analyzed all these different vegetables for glucosinolates and realized that glucobrassicin is in cruciferous vegetables, such as broccoli, cabbage, bok choi, and watercress, and there's a fair amount of it," he says.

In recent laboratory studies, Hecht and his colleagues found that two compounds that are natural breakdown products of glucobrassicin were effective chemopreventive agents in an animal model of tobacco carcinogen-induced lung cancer. They have also used proteomics to analyze the effects of these compounds on protein expression in lung tissue, with an aim of identifying proteins that could serve as new biomarkers or even targets for intervention.

Hecht's laboratory is also examining phenethyl isothiocyanate (PEITC), a compound naturally occurring in watercress, as a chemopreventive agent. His group has participated in a successful early phase clinical trial on the use of PEITC as a chemopreventive agent for lung cancer in humans. Additional work focuses on evaluating the effectiveness of using combinations of certain vegetable-based compounds for chemoprevention, although Hecht notes that it is difficult to get FDA approval for the use of combinations of compounds in clinical trials.

Soy, fish, vegetables, and green tea

Cancer Center epidemiologist Mimi Yu, Ph.D., a McKnight Presidential Professor, focuses her research on identifying dietary factors that may prevent cancer, such as soy, fish, cruciferous vegetables, and green tea (which contains cancer-preventive antioxidants known as catechins). Yu studies these factors by analyzing data from large-scale populations collected over time.

According to Yu, as researchers learn more about the influence of diet on cancer prevention, complexities are emerging. For example, Yu's research has indicated that soy intake during adolescence is protective of breast cancer risk, but that it seems to be important that the timing of soy exposure coincides with the timeframe of breast development. These results mean that a woman who adds soy to her diet at age 50 in hopes of lowering her risk of breast cancer may not see a benefit. Yu's recent research on green tea consumption provides another example of the complexity inherent in cancer prevention. She notes that although green tea consumption appears to decrease breast cancer risk in women, it is associated with increased risk of advanced colorectal cancer in men.

Yu cautions that her group's results regarding dietary influence on cancer prevention, which were largely conducted through studies of healthy individuals, are not relevant for those with cancer. Yu notes that researchers know very little about the therapeutic use of diet after cancer is diagnosed.

---

This story was originally published in the Masonic Cancer Center 2007 Annual Report.