Ovarian cancer sheds tumor suppression with loss of estrogen receptor

August 15, 2004

An important receptor for estrogen in ovarian cells has been shown to suppress tumor growth, according to a new study published in the August 15 issue of the journal Cancer Research. When ovarian tumors develop, however, the number of these receptors--known as estrogen receptor beta (ER beta)--diminishes, encouraging these tumors to advance toward malignancy and metastasis. This disappearing act may help explain why ovarian cancers are often typically resistant to anti-estrogen drugs including Tamoxifen.

"Ovarian cancer is remarkably lacking in response to antiestrogens such as Tamoxifen," Gwendal Lazennec, Ph.D., research group leader in molecular and cellular endocrinology of cancers at Inserm U540, Montpellier, France. "We hypothesized that this may be due to the selective decrease that we observed in the expression of message for ER beta in tumors from ovarian cancer patients."

Tumors from 58 ovarian cancer patients contained less messenger RNA for the ER beta than found in ovarian samples from healthy patients, said Lazennec, whose team included scientists from France and Italy. To understand how the loss of ER beta affected the ovarian cells during cancer progression, the gene for ER beta was replaced in ovarian cancer cell lines that no longer expressed the estrogen-triggered nuclear receptor. The ER beta reintroduced into the cancer cell lines did not share the classic functions attributed to estrogen receptors, including induction of progesterone receptor expression and fibuline-1C, and it's ability to decrease the expression of the cyclin D1 gene was completely opposite of it's counterpart, ER beta.

Furthermore, the restored ER beta induced apoptosis, or cell death, in the ovarian cancer cells.

"ER beta appears to have important regulatory functions in the control of the proliferation and motility of ovarian cancer," Lazennec said. "With the loss of ER beta in ovarian cells, ovarian cancers shed the restrictive properties of this steroid receptor in the regulation of cell growth, death and motility. The loss of ER beta expression appears to be an important event leading to the development of ovarian cancer."

Lazennec was joined in the ER beta studies by Aurélie Bardin, Pascale Hoffman, Françoise Vignon, Pascal Pujol, from the Unité INSERM 540, as well as Nathalie Boulle, Laboratoire de Biologie Cellulaire et Hormonale, H?pital Arnaud de Villeneuve, and Dionyssios Kasaros, Department of Obstetrics and Gynecology, via Ventimiglia, Turin, Italy.
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Founded in 1907, the American Association for Cancer Research is a professional society of more than 22,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's Annual Meetings attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.

American Association for Cancer Research

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