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A Timely Partnership

In an unusual partnership, three poultry scientists from the College of Agriculture and Life Sciences are working with Duke University researchers to learn how taking birth control pills can help reduce a woman’s chances of contracting ovarian cancer.

Petitte, Anderson, Carver and Rodriguez: The research teamUnder a research grant of $459,295 funded by the U.S. Department of Defense, Dr. James Petitte, associate professor in the department of poultry science; Dr. Kenneth Anderson, associate professor and poultry science specialist with the North Carolina Cooperative Extension Service; and Dr. Donna Carver, assistant professor and poultry science Extension veterinarian, have teamed up with Dr. Gus Rodriguez of Duke University’s Division of Gynecological Oncology to explore strategies for preventing the deadly disease.

Chickens involved in egg laying exhibit a high rate of naturally occurring ovarian cancer as they age, making them ideal research models for the disease, according to Anderson. After the age of 2, considered old for chickens, the birds show a high incidence of adenocarcinomas, or tumors, in the epithelial, or surface cells, of their ovaries.

“The chicken has a lot going for it as a model,” Petitte said. “We can use large numbers to get good statistical results.”

Investigating the advantages of progestin

Researchers have known for years that women who use oral contraceptives for as little as three years experience a 30 to 50 percent reduction in their risk of contracting ovarian cancer. They assumed that the reduced risk was correlated to a reduction in ovulation cycles brought about by oral contraceptives, but they were beginning to explore the idea that “the pill” might have some other preventive effect.

Duke researchers conducted a study involving monkeys who took oral contraceptives containing progestins for three years. At the end of the study, the monkeys’ ovaries were examined.

"What we found was that monkeys exposed to progestins had a significant incidence of apoptosis in the lining of the ovary,” Rodriguez said

Apoptosis occurs when a cell undergoes irreparable damage, causing the cell to kill itself. The researchers now believe that this could be the major advantage of taking progestins, which may cause the ovarian lining to rid itself of cells that could cause cancer.

The N.C. State researchers have demonstrated that the chicken is a good model for studying ovarian cancer prevention. Now they hope to learn what strategies for taking progestins are most effective in further reducing the rate of ovarian cancer.

“Our end goal is to generate a working model that people could use to develop prevention methods for ovarian cancer in women,” Anderson said. “Right now, we’re looking at progestins, which women take as birth control.”

“If routine use of the pill for three years can so dramatically reduce ovarian cancer in women, we could possibly develop a regimen that could reduce the rate by more than 50 percent, which is already a remarkable amount,” Rodriguez said.

The ovarian epithelial cells of chickens and humans are very similar, according to Anderson. Poultry science researchers have discovered that progestins affect these tissues in chickens the same way they do in humans.

Since ovarian cancers occur most often in post-menopausal women who have stopped ovulating, the researchers manipulated the chickens’ diet and reduced their weight to mimic menopause by preventing egg laying.

Now the researchers are testing different regimens of taking progestins to determine their effectiveness in preventing cancer. As the research chickens die, necropsies are conducted to examine their ovaries for signs of cancer.

The study is being conducted at the Piedmont Research Station near Salisbury, in conjunction with the North Carolina Department of Agriculture and Consumer Services. Hens that age out of the North Carolina Layer Performance and Management Test are just the right age for the cancer study.

Better health for women -- and more

Carver, the Extension veterinarian who is conducting necropsies of birds in the study, said she is excited to be involved in a project that may lead to better health for women.

“Women’s health issues have not been studied enough,” she said. “Ovarian cancer tumors are very fast-growing. Once you discover it, the cancer often appears somewhere else.”

Ovarian cancer causes more deaths than all other gynecological cancers combined. Each year in the United States, 27,000 to 28,000 women are diagnosed with the disease, and 16,000 to 17,000 women die from it. Despite progress made in treating cancers, most women who contract ovarian cancer will die from it. The disease is not easily detected and is often discovered in an advanced stage.

In addition to the human health benefits from this research, Petitte says there will be benefits to agriculture as well. The study could lead to new strategies for managing older hens. Egg laying in commercial hens drops after the age of 2, and most hens are retired by age 2.5 years. In one study group, birds receiving progestins actually increased their egg laying, Petitte said.

Carver likewise noted that, because there is actually very little literature on the incidence of ovarian cancer in chickens, the research will lend the added benefit of a better understanding of cancer in chickens.