UNM Discovery Could Help Fight Breast, Uterine Cancers
The Associated Press
A discovery by New Mexico researchers could someday lead to better treatments for breast and uterine cancers.
Researchers from the University of New Mexico and a chemist from New Mexico State University discovered an added complexity in the way some breast cancers react to estrogen.
That might explain why standard treatments for breast cancer sometimes aren't as effective as they should be, said Eric Prossnitz, a UNM associate professor of cell biology and physiology.
The group's research is published in Science Magazine's Feb. 10 edition.
In cancer, the function of estrogen to regulate cell growth in certain organs gets distorted, Prossnitz said.
"For many years, doctors have treated breast cancer based on how cells in the tumor bind to estrogen," he said. "During that time, it was thought there were two types of ways it binds. In one, with what we call positive receptors, estrogen binds with parts of the cell and helps a tumor grow. In the other, with what we call negative receptors, there appears to be other factors making the tumor grow."
The scientists proved there is a third receptor that binds to estrogen in a different way, complicating treatment and the effectiveness of certain drugs, Prossnitz said.
"This is a completely new pathway influencing tumors," said UNM cancer researcher Larry Sklar. "What this means is all the other treatment information is incomplete, because this pathway hasn't been factored into the way doctors think about treating cancer."
Scientists can now move forward to study the third receptor, Prossnitz said.
"From there, hopefully what we learn can be used by doctors to alter the way to treat breast and uterine cancer patients," he said. "We might even see that in the next few years."
Doctors use a drug, tamoxifen, for breast cancer that has positive estrogen receptors. Tamoxifen binds to those receptors, blocking estrogen so the tumor grows more slowly or stops. Cancers with negative receptors use different drugs or treatments that don't deal with estrogen, Prossnitz said.
The third receptor binds to estrogen in a different way, so drugs like tamoxifen might not be as effective, Prossnitz said.
"One example of how that might change treatment strategies is that there's a slightly higher incidence of uterine cancer in women treated with tamoxifen for breast cancer," he said. "What we know so far is that although tamoxifen blocks the classic positive estrogen receptor, it actually activates this new one. That might be causing the uterine cancer, although that's just speculation right now."
In other cases, the new receptor could explain why tamoxifen sometimes doesn't work and why tumors with negative receptors sometimes respond to estrogen, he said.
"As far as we know, all these receptors are present in everyone, but cancer changes the way they work," Prossnitz said. "What we still have to study is how they change in a cancer and what they're actually doing."
Up next: to continue looking at how the receptor works normally and to look at certain cancers to see if the receptor's function is altered in certain ways, he said.
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