New test suggests antidepressant Paxil may promote breast cancer

February 21, 2014

A team of researchers from the City of Hope in Duarte, Calif., has developed a speedy way to identify drugs and chemicals that can disrupt the balance of sex hormones in human beings and influence the development and progress of diseases such as breast cancer.

In a trial screening of 446 drugs in wide circulation, the new assay singled out the popular antidepressant paroxetine (better known by its commercial name, Paxil) as having a weak estrogenic effect that could promote the development and growth of in women.

This is important because as many as a quarter of women being treated for suffer from depression - a condition most commonly treated with antidepressants known as SSRIs (selective serotonin reuptake inhibitors), including Paxil, which has been on the market since 1992. Almost a quarter of American women in their 40s and 50s are taking an antidepressant, mostly SSRIs.

Last summer, the Food and Drug Administration approved the marketing of a low dose of paroxetine - repackaged under the commercial name Brisdelle - as a nonhormonal treatment for hot flashes and other menopausal symptoms.

About 70 percent of breast cancers in women are sensitive to estrogen, meaning that the hormone found plentifully in females of child-bearing age contributes to their growth.

The novel screening method developed at City of Hope, described in a forthcoming issue of the journal Toxicological Sciences, also identified two antifungal medications - biconazole and oxyconazole - as having an anti-estrogenic effect similar to that of medications prescribed to prevent breast cancer and its recurrences in women. Incidental to their intended use in combating fungal infections, those medications inhibit the action of aromatase, an enzyme that converts androgens - hormones more plentiful in males but present in both sexes - into estrogen.

Less surprising, the high-throughput screening mechanism identified bisphenol A - a compound used in the manufacture of plastics and epoxy resins - as an estrogen promoter capable of raising .

The discovery that Paxil behaves as an endocrine-disrupting chemical may shed light on growing suspicions about the medication in women who have had breast cancer. A 2010 study found that in Canada who were taking Paxil were more likely than those taking other antidepressants to die of breast cancer when there was a substantial overlap in their use of that antidepressant and of tamoxifen to prevent .

The researchers surmised that paroxetine, which was taken by about a quarter of the depressed breast cancer patients in the study, might block the production of a liver enzyme needed to metabolize tamoxifen. The authors of the latest research said paroxetine's "weak estrogenic" effect "may be responsible, in part, for the observed reduction" in tamoxifen's effectiveness in that study.

The finding that paroxetine has estrogenic effects "has implications for patients with estrogen-sensitive breast cancer who are on other medications," said Shihuan Chen, professor and chairman of City of Hope's department of cancer biology and lead author of the study.

To confirm paroxetine's estrogenic action, the researchers performed a further analysis that found that many of the genes whose activity is altered by paroxetine are genes that also respond to estrogen. But the researchers said the assay does not show whether the antidepressant medication alters the activity of estrogen directly or by indirect means.

Explore further: First non-hormonal remedy approved for menopausal hot flashes

Related Stories

First non-hormonal remedy approved for menopausal hot flashes

July 1, 2013
(HealthDay)—Brisdelle (paroxetine) has been approved by the U.S. Food and Drug Administration as the first non-hormonal treatment to treat hot flashes associated with menopause.

Osteoporosis drug may treat breast and liver cancers

February 19, 2014
(Medical Xpress)—A drug used to prevent and treat osteoporosis in post-menopausal women may also be able to treat some breast and liver cancers, according to a new study from Oregon State University.

First in-human trial of endoxifen shows promise as breast cancer treatment

December 12, 2013
A Phase I trial of endoxifen, an active metabolite of the cancer drug tamoxifen, indicates that the experimental drug is safe, with early evidence for anti-tumor activity, a Mayo Clinic study has found. The findings indicate ...

Smoking linked with increased risk of most common type of breast cancer

February 10, 2014
Young women who smoke and have been smoking a pack a day for a decade or more have a significantly increased risk of developing the most common type of breast cancer. That is the finding of an analysis published early online ...

USPSTF: Offer breast CA risk-reducing Rx to high-risk patients

September 24, 2013
(HealthDay)—The U.S. Preventive Services Task Force (USPSTF) recommends that women at increased risk of breast cancer be prescribed tamoxifen or raloxifene for risk reduction, according to a final Recommendation Statement ...

Recommended for you

Single blood test screens for eight cancer types

January 18, 2018
Johns Hopkins Kimmel Cancer Center researchers developed a single blood test that screens for eight common cancer types and helps identify the location of the cancer.

Researchers find a way to 'starve' cancer

January 18, 2018
Researchers at Vanderbilt University Medical Center (VUMC) have demonstrated for the first time that it is possible to starve a tumor and stop its growth with a newly discovered small compound that blocks uptake of the vital ...

How cancer metastasis happens: Researchers reveal a key mechanism

January 18, 2018
Cancer metastasis, the migration of cells from a primary tumor to form distant tumors in the body, can be triggered by a chronic leakage of DNA within tumor cells, according to a team led by Weill Cornell Medicine and Memorial ...

Modular gene enhancer promotes leukemia and regulates effectiveness of chemotherapy

January 18, 2018
Every day, billions of new blood cells are generated in the bone marrow. The gene Myc is known to play an important role in this process, and is also known to play a role in cancer. Scientists from the German Cancer Research ...

These foods may up your odds for colon cancer

January 18, 2018
(HealthDay)—Chowing down on red meat, white bread and sugar-laden drinks might increase your long-term risk of colon cancer, a new study suggests.

The pill lowers ovarian cancer risk, even for smokers

January 18, 2018
(HealthDay)—It's known that use of the birth control pill is tied to lower odds for ovarian cancer, but new research shows the benefit extends to smokers or women who are obese.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.