The National Cancer Institute has renewed its support for the landmark California Teachers Study through a five-year, $16.8 million grant. The project is led by Leslie Bernstein, Ph.D., director of City of Hope’s Division of Cancer Etiology.

Leslie Bernstein is principal investigator on the influential California Teachers Study. (Photo by Walter Urie)

For more than a decade, the study has shined new light on factors that can affect women’s health, such as obesity, physical activity, diet and use of medications. The grant will enable scientists to delve deeper into the lifestyle and genetic factors that may influence cancer risk — and provide evidence for public health efforts that may potentially help millions.

The California Teachers Study includes nearly 133,500 female teachers and administrators in the California public schools’ retirement system. Researchers began following the study participants in 1995, periodically monitoring their health status, height and weight. They also ask about their habits, including their exercise patterns and use of alcohol and hormone replacement therapy, oral contraceptives and other drugs.

Because researchers have access to California’s statewide cancer registry and hospitalization data, they can obtain important health information, such as cancer diagnoses, births and surgeries, related to their study participants. The combination of data about risk factors and health outcomes over a long period makes the study particularly powerful.

“Over the last decade, we’ve seen many changes in the factors associated with breast and other cancers in women. In the next five years, the California Teachers Study will allow us to learn much more about how variations in women’s genes interact with these lifestyle factors to influence risk,” Bernstein said.

The researchers will focus on three areas of societal change: physical activity, obesity and aspirin use.

Physical activity

People worldwide are becoming less physically active, their once-active hobbies replaced by TV viewing and Internet surfing. Yet researchers have shown that getting plenty of exercise can reduce risk of breast and colon cancer — as well as other problems such as cardiovascular disease and diabetes — so health experts recommend regular physical activity.

According to Bernstein, exercise participation and benefits from these activities might be linked to variations in certain genes associated with fitness, endurance and athletic ability. Through the study, researchers will examine the relationship between these gene variants, physical activity and breast cancer risk — a topic that has never been studied.

Obesity

Many women today are struggling to lose their extra pounds. Obesity rates are soaring, likely increasing future cancer rates, too. Under the California Teachers Study, scientists will look at patterns of changes in body fat over a lifetime and how being obese or overweight is associated with common forms of breast, endometrial and colon cancers.

Since disease risk stems from more than obesity, though, the researchers also will investigate how other cancer risk factors like physical activity, hormone therapy and oral contraceptive use, eating and drinking habits, diabetes, smoking and menopausal status can modify relationships between obesity and these cancers.

Aspirin use

Physicians today offer drugs like tamoxifen to help prevent breast cancer among breast cancer survivors and women at high risk for the disease, but these drugs offer little benefit for the average woman. They need other options that are safe, simple and inexpensive. One possibility is aspirin.

Many women already take low doses of aspirin to cut their risk of cardiovascular disease, so California Teachers Study researchers will examine this aspirin use and look for links to breast cancer risk. They hope to see whether aspirin can modify breast cancer risk linked to use of hormone therapy and other factors, and if it has effects on any subtype of breast cancer in particular.

The researchers also will examine whether variants in genes related to inflammation, immune function and insulin resistance interact with aspirin use, obesity or physical activity to influence breast cancer risk.

“We’re excited about this work, because we will be looking at risk factors that are modifiable. These are steps that could help prevent cancer population-wide,” Bernstein said.

The study will involve City of Hope researchers Katherine D. Henderson, Ph.D., Sophia Wang, Ph.D., James V. Lacey Jr., Ph.D., Huiyan Ma, Ph.D., Yani Lu, Ph.D., and Christina Dieli-Conwright, Ph.D. Collaborating cancer researchers in California include epidemiologists and biostatisticians at the University of Southern California, University of California Irvine and Cancer Prevention Center of California.

For more information on the California Teachers Study, visit www.calteachersstudy.org.