Carcinogenicity of estrogens in human breast epithelial cells

image of breast epithelial cells

DES induces in HBEC phenotypic changes indicative of cell transformation, associated with significant genomic alterations

2001 Study Abstract

Epidemiological and clinical evidences indicate that breast cancer risk is associated with prolonged ovarian function that results in elevated circulating levels of steroid hormones. Principal among these is estrogen, which is associated with two important risk factors, early onset of menarche and late menopause.

However, up to now there is no direct experimental evidence that estrogens are responsible of the initiation of human breast cancer. We postulate that if estrogens are causative agents of this disease, they should elicit in human breast epithelial cells (HBEC) genomic alterations similar to those exhibited by human breast cancers, such as DNA amplification and loss of genetic material representing tumor suppressor genes. These effects could result from binding of the hormone to its nuclear receptors (ER) or from its metabolic activation to reactive metabolites.

This hypothesis was tested by treating with the natural estrogen 17beta-estradiol (E2) and the synthetic steroid diethylstilbestrol (DES) MCF-10F cells, a HBEC line that is negative for ER. Cells treated with the chemical carcinogen benzo (a) pyrene (BP) served as a positive control of cell transformation.

BP-, E2-, and DES-treated MCF-10F cells showed increases in survival efficiency and colony efficiency in agar methocel, and loss of ductulogenic capacity in collagen gel. The largest colonies were formed by BP-treated cells, becoming progressively smaller in DES- and E2-treated cells. The loss of ductulogenic capacity was maximal in BP-, and less prominent in E2- and DES-treated cells. Genomic analysis revealed that E2- and DES-treated cells exhibited loss of heterozygosity in chromosomes 3 and 11, at 3p21, 3p21-21.2, 3p21.1-14.2, and 3p14.2 14.1, and at 11q23.3 and 11q23.1-25 regions, respectively. It is noteworthy that these loci are also affected in breast lesions, such as ductal hyperplasia, carcinoma in situ, and invasive carcinoma.

Our data are the first ones to demonstrate that estrogens induce in HBEC phenotypic changes indicative of cell transformation and that those changes are associated with significant genomic alterations that might unravel new pathways in the initiation of breast cancer.


  • Carcinogenicity of estrogens in human breast epithelial cells, APMIS : acta pathologica, microbiologica, et immunologica Scandinavica, NCBI PubMed PMID: 11297193, 2001 Jan.
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The “morning-after pill”

The use of diethylstilbestrol (DES) as a postcoital contraceptive agent is discussed

A course of post-coital estrogens, in adequate dosage, is a highly effective and safe (though misnamed) form of post-coital contraception that deserves to be more widely known and prescribed. Both unwanted pregnancies and the demand for abortion could be reduced by its widespread use in emergency situations.

Several natural and synthetic estrogens have been used in various dosages; a popular regimen is 5 milligrams of stilbestrol, 5 times per day for 5 days, preferably accompanied by an anti-emetic, since nausea and occasional vomiting may occur.

Some authorities advise starting the course of estrogens within 48 hours of unprotected intercourse and others set a reliable outside limit of 72 hours, turning a Friday night indiscretion into a Monday morning routine appointment rather than a weekend emergency.

For a series of 30 cases started on the above dosage within 72 hours of coitus without contraception or with condom failure, I am able to report no pregnancies. These patients proved particularly responsive to counselling, almost all keeping subsequent appointments for a more satisfactory method of birth control.

Similar success was reported verbally at the recent American College Health Association conference1 by a gynecologist from Yale.

An interim report from the University of Utrecht indicated no failures in 72 women using post-coital estrogens, and a comprehensive review of the literature on the subject, with an analysis of 1000 cases, is to be presented by the same author at the forthcoming Fertility-Sterility Conference in Tokyo in October.

Professor Haspels’ excellent paper should do much to clear up the confusion that exists in many minds between this highly reliable method of post-coital contraception and the virtually useless attempts that are sometimes made to terminate a pregnancy by administering estrogens after a missed menstrual period.

This subject is, of course, unrelated to the use of prostaglandins, which is an entirely different story.


  • The “morning-after pill”, Canadian Medical Association journal, NCBI PubMed PMC1931140, 1971 Aug 7.

DES Research Heats Up Again After Breast Cancer Finding

Journal of the National Cancer Institute, August 1999

“Based on continued cohort studies, we are now fairly sure that DES women face a 20% to 30% excess risk for breast cancer,”

Robert Hoover, M.D., director of the Epidemiology and Biostatistics Program at the National Cancer Institute

“DES could serve the study of other potential estrogenic cancer-causing compounds and environmental estrogens — none are as potent as DES and it would make an excellent model,”

Retha Newbold, head of the Developmental Endocrinology Section at the National Institute of Environmental Health Sciences, Research Triangle Park, N.C.

Another recommendation from the group was that researchers start to examine grandchildren of DES-exposed women, as they too may have a potential for DES cancers.

Read the full paper DES Research Heats Up Again After Breast Cancer Finding on Oxford University Press, 18 August 1999.


Maternal factors and breast cancer risk among young women

Intrauterine DES exposure and subsequent risk of breast cancer

1998 Study Abstract

The results from previous studies have provided evidence to support the hypothesised association between intrauterine oestrogen exposure and subsequent risk of breast cancer. Information has not been available to study this relationship for several perinatal factors thought to be related to pregnancy oestrogen levels.

Data collected from the mothers of women in two population-based case-control studies of breast cancer in women under the age of 45 years (510 case mothers, 436 control mothers) who were diagnosed between 1983 and 1992 in three western Washington counties were used to investigate further the relationship between intrauterine oestrogen exposure and risk of breast cancer.

A pregnancy weight gain of 25-34 pounds was associated with breast cancer risk (odds ratio [OR] = 1.5; 95% confidence interval [CI] 1.1, 2.0); however, women whose mothers gained 35 pounds or more were not at increased risk. Use of antiemetic medication in women with any nausea and vomiting (OR = 2.9; 95% CI 1.1, 8.1) and use of diethylstilboestrol (DES) (OR = 2.3; 95% CI 0.8, 6.4) appeared to be positively associated with breast cancer risk.

The results from this study provide limited support for the hypothesis that in utero oestrogen exposure may be related to subsequent breast cancer risk among young women.


  • Maternal factors and breast cancer risk among young women, Paediatric and perinatal epidemiology, NCBI PubMed PMID: 9805713, 1998 Oct.
  • Image credit Asdrubal luna.

Postcoital contraception : present and future options

DES still used for emergency contraception in 1995


This article reviews information on currently available postcoital contraceptives, and discusses recent advances in postcoital contraception, mostly notably RU 486.

Postcoital contraceptives, or “morning after pills,” are currently available in the form of high dose estrogens, oral contraceptives, danazol and intrauterine devices. These methods are plagued by high incidences of side effects and less than optimal success rates.

Currently, their primary use in the adolescent age group is for victims of sexual assault, but they may also be used as back-up for consensual unprotected intercourse. RU 486, best known as a first trimester abortifacient, has a number of potential uses, including that of a postcoital contraceptive. Two recently published studies from the UK showed RU 486 to have a very low pregnancy rate and fewer side effects when compared with current methods. RU 486 may someday replace high doses of oral contraceptives as the method of choice for postcoital contraception.

Postcoital contraceptives are available for adolescent use in the US. They include combination oral contraceptives (OCs), high dose estrogens, danazol, and IUDs. Mifepristone (RU-486) is currently not available in the US but is used in France, the UK, and Sweden. Postcoital contraception is especially important for adolescents who have a very high pregnancy rate due to poor contraceptive use. Administration of 2-5 mg ethinyl estradiol (EE) for 5 days beginning within 72 hours of unprotected intercourse yields pregnancy rates ranging from 0-0.92%. EE-related side effects include nausea, vomiting, sore breasts, and irregular menstrual bleeding. DES should not be used, since it is associated with reproductive tract anomalies and vaginal cancers in exposed offspring. Conjugated estrogens have not been used in adolescents for postcoital contraception. The Yuzpe regimen consists of 2 tablets of a combined OC with 200 mg EE and 2 mg dl-norgestrel administered within 72 hours of unprotected intercourse followed by the same dose 12 hours later. Common side effects are nausea and vomiting. Its pregnancy rate is 1.8%. Levonorgestrel-containing OCs can also be used. Administration of 800-1200 mg danazol up to 120 hours after unprotected intercourse protects against pregnancy in about 98% of cases. Copper IUDs have a high efficacy rate when used as postcoital contraception (99.9%), but public opinion, medicolegal considerations, financial costs, and potential for infection impede IUD as a postcoital contraceptive in the US. RU-486 is best known as an abortifacient. It is also a potential postcoital contraceptive. Two UK studies find that RU-486 used as a postcoital contraceptive has a very low pregnancy rate and fewer side effects than the Yuzpe regimen and danazol. It is much more costly than currently used postcoital contraceptives (600 mg of RU-486 cost US$ 68, while Ovral costs US$ 0.48-2.24). Nevertheless, RU-486 may replace the higher doses of OCs as a postcoital contraceptive method.


  • Postcoital contraception: present and future options, The Journal of adolescent health : official publication of the Society for Adolescent Medicine, NCBI PubMed PMID: 7742340, 1995 Jan.

DES and breast cancer risk

Experimental study on relationship between exogenous estrogen and breast cancer risk

1997 Study Abstract

To investigate the relationship between exogenous estrogen and breast cancer risk.

Female rats were randomly divided into three groups, namely diethylstilbestrol (DES), norethindrone compositae (CoNET) and control group. The histological structure and ultrastructural changes of mammae were observed. The levels of sexual hormones in serum were determined and the AgNOR counts, DNA contents and steroid receptor contents in mammary epithelium were also detected.

In DES group, the level of progesterone (10.38 ng/ml) was obviously lower than that in the control group (13.37 ng/ml); the incidence of hyperplasia of mammary gland (73.33%) was significantly higher than that in the control group (7.69%); and the degree of hyperplasia was obviously more serious than that in the control group. Moreover, there were 13.33% of rats with atypical hyperplasia in DES group. The DNA contents, AgNOR counts and estrogen receptor (ER) positive rate were markedly higher in DES group (95.60, 2.43 and 71.71% respectively) than in the control group (83.07, 1.88 and 40% respectively). However, in CoNET group, there were no obvious influences on ER, AgNOR and DNA in mammary epithelium.

Exogenous estrogen (DES) could affect the levels of sexual hormones in serum, accelerate the DNA duplication, increase the AgNOR counts and ER contents, and induce atypical hyperplasia and ultrastructural changes of mammary gland, hence becoming a latent risk factor of breast cancer. However, the results failed to suggest that the contraceptive, CoNET, could increase the risk of breast cancer.


  • Experimental study on relationship between exogenous estrogen and breast cancer risk, Chinese medical journal, NCBI PubMed PMID: 9594309, 1997 May.

Emergency contraception : 1994 review

Diethylstilbestrol used as a “morning after” contraceptive


In the Netherlands, many women use a postcoital method of contraception in “emergency” situations.

Postcoital contraception started in the 1960’s with the administration of large doses of estrogens: 50 mg diethylstilbestrol for 5 days or 5 mg ethinylestradiol for 5 days.

In the eighties, a double-blind study compared the original hormonal therapy of 5 mg ethinylestradiol for 5 days with a combination pill containing just 0.1 mg in combination with 1 mg d1-norgestrel, of which two doses are give, the second 12 hours after the first. This method was as effective in preventing pregnancy as the original treatment with high estrogen dosage. Moreover, it resulted in women suffering less nausea and vomiting. One study from Hong Kong indicated that levonorgestrel without ethinylestradiol was as effective as the combination. Postcoital use of an intrauterine device to prevent pregnancy can be used as an alternative to the hormonal method. A recent development is the use of an antiprogestagen pill: 600 mg Mifepristone on day 27 of the cycle; side effects are minimal and the success rate is high. Mifepristone should be registered and made available in all countries for this indication.


Many women in the Netherlands depend on a postcoital contraceptive (PCC) method in situations of unprotected intercourse. The incidence rate for abortions and for adolescent pregnancies in the Netherlands is the lowest worldwide. Dutch society matter-of-factly accepts adolescent sexuality and provides formal and informal sex education and readily accessible contraceptive services. Emergency contraception should be administered within 72 hours after unprotected intercourse (e.g., rape or incest) or mechanical contraceptive failure. Administration of 5 mg ethinyl estradiol (EE) for 5 days as a PCC first occurred in the Netherlands in 1964, and PCC usage peaked at 55,000 in 1975. Side effects of EE include, in order of frequency, nausea, vomiting, tender breasts, and menorrhagia. Possible modes of action for EE are more rapid transport of fertilized ova through the oviduct and slowed maturation of the endometrium, resulting in suppressed implantation. The Yuzpe PCC method involves 4 tablets of a combined oral contraceptive (each tablet with 50 mcg EE + 250 mcg levonorgestrel) administered within 72 hours followed by 2 tablets 12 hours later. Side effects are similar to those of EE alone, as is the effectiveness rate. A dose of 0.75 mg levonorgestrel alone is as effective at preventing pregnancy as the Yuzpe regimen. Side effects are considerably less common with the levonorgestrel regimen than the Yuzpe regimen. For women who present more than 72 hours after and less than 7 days after unprotected intercourse or for those with contraindications to estrogen, a copper-releasing IUD can serve as a PCC. A postcoital IUD can cause serious complications for women with a sexually transmitted disease, however. Taking RU-486 during the luteal phase of the menstrual cycle greatly drops plasma levels of progesterone and estradiol. Postovulatory administration of an antiprogestogen is the best PCC method because of minimal side effects and a high success rate.



Prenatal and perinatal risk factors for breast cancer in young women

There is increasing interest in the role of early life exposures in breast carcinogenesis, especially estrogen exposure in utero

1997 Study Abstract

Estrogen levels during pregnancy may be higher in twin pregnancies and among older women and slightly lower among smokers.

We analyzed early life risk factors in a population-based case-control study in the United States of 2,202 breast cancer cases and 2,009 controls under age 55 years. Twins were at an increased risk of breast cancer compared with singletons (relative risk = 1.62; 95% confidence interval = 1.0-2.7), particularly women with a twin brother (relative risk = 2.06), a finding consistent with the observation of high estrogen levels in dizygotic twin pregnancies. Little association was seen between maternal age at birth and breast cancer risk.

We carried out further analyses for 534 cases and 497 controls under age 45 years, using data from a questionnaire completed by their mothers relating to the daughters’ early life exposures. There was no evidence of an effect of smoking or diethylstilbestrol exposure during pregnancy on daughters’ breast cancer risk. A reduced breast cancer risk was seen among women who had been breastfed (relative risk = 0.74; 95% confidence interval = 0.6-1.0).

These findings indicate some effect of early life exposures on breast cancer risk, although the role of estrogen exposure may be less central than previously suggested.


  • Prenatal and perinatal risk factors for breast cancer in young women, Epidemiology, NCBI PubMed PMID: 9229211, 1997 Mar.
  • Featured image Jakob.

Postcoital contraception underrecognized and underutilized

Diethylstilbestrol as a “morning after” contraceptive

1992 Study Abstract

Postcoital contraception can play an important role in the prevention of unwanted adolescent pregnancy in the US.

Diethylstilbestrol (DES), 25 mg twice daily for 5 days within 24 to a maximum of 72 hours after unprotected sexual intercourse, received US Food and Drug Administration (FDA) approval for pregnancy prevention in 1973.

In 1978, however, the manufacturer, Eli Lilly, included in its packaging instructions that DES should not be used for postcoital contraception given the development of clear-cell adenocarcinoma of the vagina or cervix in the daughters of women who took DES to prevent spontaneous abortion.

The FDA had not withdrawn its approval of DES for this purpose. Other drugs that have been effectively used for postcoital contraception include 0.5 mg of norgestrel and 0.05 mg of ethinyl estradiol (2 tablets within 72 hours of unprotected intercourse and another 2 tablets 12 hours later) and conjugated estrogens.

This approach to pregnancy prevention sidesteps many of the medical and moral complexities associated with use of the abortifacient RU-486. In fact, the Catholic bishops of Great Britain have approved the use of postcoital contraception in women who are victims of sexual assault.


  • Postcoital contraception underrecognized and underutilized, Female Patient, NCBI PubMed PMID: 12287765, 1992 Jun.
  • Featured image bunchfamily.