Drug News
Study confirms hormone-induced breast cancer risk
By Ben Wasserman
Apr 1, 2008 - 1:57:20 PM

TUESDAY April 1, 2008 (foodconsumer.org) -- A U.S. study suggests a synthetic hormone commonly used in hormone replacement therapy indicated to ease symptoms associated with menopause may place a major role in the increased risk for breast cancer.

Researchers from the University of Missouri not only revealed progestin could be a major factor in promoting breast cancer, also discovered evidence that using an antibody known as PRIMA that prevents new blood vessel formation in tumors can ward off the negative effects of the hormone.

In a study published in the journal, Cancer Research, Salman Hyder and team found exposing tumor cells to progestin increased production of a growth factor involved in the formation of new blood vessels in tumors.

Tumors need blood vessels for proliferation and growth.   Increasing the blood supply allows the tumors to grow.

But the growth factor can be suppressed using PRIMA, which re-activated a protein known as p53 and reduced the number of breast cancer cells, the researchers found.

"As women age, many develop tiny lesions in their breasts," said Hyder, professor of biomedical sciences in the College of Veterinary Medicine and the Dalton Cardiovascular Research Center.

Most of the time, Hyder said, these lesions never develop into breast cancer, probably due to the presence of p53, which prevents tumor cells from living.

"We found in our study that when the protein is active, it reduces the number of breast cancer cells in the body by inhibiting the growth factor that supplies blood vessels to the tumor. However, when the cells of these lesions are exposed to progestin in a body that does not have an active p53 protein, we found that the cells might start expanding and turn into tumors," Hyder said.

The hormone used in the study is known as medroxyprogesterone acetate (MPA), which is commonly used in HRT.

In the study, the researchers found human breast cancer cells in animals grew at an accelerated rate after MPA was introduced to the animals.

But when the cells were exposed to the antibody known as 2C3 or PRIMA, they failed to grow and spread in response to the MPA.

"Since MPA is a synthetic hormone, it stays in the body longer," Hyder said. "Unfortunately, while the drug is used to protect the uterus from the harmful effects of estrogens in HRT formulations, it is hurting the breast."

An early study showed that even a few years after patients stopped using synthetic hormones, the increased risk of breast cancer persists.

The increased risk for breast cancer was initially found in The Women’s Health Initiative Study.  Those who were treated with estrogen/progestin were at a 26 percent increased risk for breast cancer.

Hormone therapy can also increase risk of cardiovascular disease in addition to breast cancer.

Hyder believed many women have a p53 protein, but its not active and unable to inhibit MPA-induced growth factor that promotes proliferation of the tumor cells.