Stripping a layer of cells from the ovaries of rhesus monkeys did not affect the function of their ovaries, a new study says. The layer, called ovarian surface epithelium, is thought to be a possible breeding ground for ovarian cancer in humans.
Removing the ovarian surface epithelium from the monkeys' ovaries didn't affect the ovaries' normal cyclic patterns, egg production or production of estrogen and progesterone, the study said. Scientists removed the layer of cells using minimally invasive surgery.
While more research is needed, the basic findings could be promising for women at high risk for ovarian cancer who want to preserve their ability to have children and who don’t want to remove their ovaries as a preventative measure, said study researcher Jay Wright, a scientist in the Division of Reproductive Sciences at the Oregon National Primate Research Center at Oregon Health & Science University.
High-risk women include those with the BRCA gene mutation , a known risk factor for breast and ovarian cancer, or those with a family history of the cancer, Wright said.
The idea is that in the future, women may be able to have the ovarian surface epithelium removed from their ovaries to decrease — though probably not eliminate — the risk of cancer, Wright said.
However, this implication hinges largely on the assumption that ovarian cancer originates on the ovarian surface epithelium, a widely held but unproved belief, he said.
Other experts are more skeptical, saying that a lot more research is needed before the results can be implicated for ovarian cancer patients. However, they say it's promising that researchers found monkeys may be good models for studying ovarian cancer. (Ovarian cancer is notoriously difficult to study in animal models, because not many animals develop the cancer.)
“I think this data supports further studies in a monkey model to test hypotheses of ovarian cancer development, which could teach us something about tumor biology, but I don't think it's specific to any particular population of women with ovarian cancer as it stands now ” said Dr. Sarah Adams, assistant professor of gynecologic oncology at Pennsylvania Hospital at the University of Pennsylvania, who was not involved with the study.
The study is published in the current online issue of the journal Human Reproduction.
Hinging on a hypothesis
One of the prevailing theories in ovarian cancer genesis is that ovarian cancer stems from the ovarian surface epithelium. This layer of cells isn't known to have any function in humans, but in other animals it helps to protect the ovaries from scarring during ovulation, Wright said.
Seventy percent of ovarian cancers originate on the ovarian surface epithelium, said Dr. Sarah Temkin, assistant professor of obstetrics, gynecology and reproductive sciences at the University of Maryland Medical Center, who was not involved with the study.
“But there's never been a precursor lesion [the beginning sign of cancer] that's been identified on the ovary,” Temkin told MyHealthNewsDaily. “So it's never been proven that this is where ovarian cancer starts, although this is the most widely accepted theory of the development.”
However, precursor lesions have been found on the fimbriae (fingerlike projections) of the fallopian tube, which transport eggs from the ovaries to the uterus, she said.
An emerging theory is that the fimbriae, which touch the ovaries, are actually where ovarian cancer originates, Temkin said.
For the new study to apply to humans, it must be proven that ovarian cancer does in fact originate in the cells that make up the ovarian surface epithelium, and is not just discovered there because the ovarian surface epithelium is near the fimbriae of the fallopian tube, she said.
Wright acknowledged the same caveat. He found in his study that after stripping the ovarian surface epithelium from the monkeys' ovaries, a few cells remained on the ovaries. Wright said more research must be done to determine if the cells are ovarian surface epithelium cells that grew back, or if they're cells from the fimbriae that were transferred over to the ovaries.
Who's at stake?
Ovarian cancer is the eighth most common cancer in women in the United States, and the fifth leading cause of cancer death in women, according to the Centers for Disease Control and Prevention. When caught early, the survival rate is very high. But symptoms are often vague, making it hard to catch before it progresses to a more advanced stage .
Right now, women who are at high risk for ovarian cancer are advised to undergo an oophorectomy — removal of the ovaries — as well as the fallopian tubes, Adams said. Many women at risk for ovarian cancer undergo an oophorectomy after they are finished with childbearing.
“This is a very difficult decision for many women who do not have cancer but are at high risk” for developing it, Adams told MyHealthNewsDaily, though research has shown that the risk of cancer drops by 96 percent after oophorectomy.
In women with a cancer diagnosis, oophorectomy is an important part of treatment. If a woman has cancer confined to one ovary, it is sometimes possible to leave the healthy ovary behind and preserve fertility, but this must be done on a case-by-case basis and with a thorough understanding of the risks and benefits involved, she said.
Because preservation of fertility is the ultimate goal of the research, Wright and his colleagues plan to do additional studies to see if the monkeys whose ovaries were stripped of the ovarian surface endothelium are able to breed and have offspring.
Pass it on: Scientists are doing research in monkeys to see if there's a way for women at high risk of ovarian cancer to keep their ovaries so they can preserve their fertility.
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