Short-term exposure to pregnancy levels of estrogen prevents mammary carcinogenesis

Citation
L. Rajkumar et al., Short-term exposure to pregnancy levels of estrogen prevents mammary carcinogenesis, P NAS US, 98(20), 2001, pp. 11755-11759
Citations number
46
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN journal
0027-8424 → ACNP
Volume
98
Issue
20
Year of publication
2001
Pages
11755 - 11759
Database
ISI
SICI code
0027-8424(20010925)98:20<11755:SETPLO>2.0.ZU;2-O
Abstract
It is well established that pregnancy early in life reduces the risk of bre ast cancer in women and that this effect is universal. This phenomenon of p arity protection against mammary cancer is also observed in rodents. Earlie r studies have demonstrated that shortterm administration of estradiol (E) in combination with progesterone mimics the protective effect of parity in rats. In this study, the lowest effective E dosage for preventing mammary c ancer was determined. Rats were injected with N-methyl-N-nitrosourea at 7 w eeks of age; 2 weeks later, the rats were subjected to sustained treatment with 20 mug, 100 mug, 200 mug, or 30 mg of E in silastic capsules for 3 wee ks. Treatments with 100 mug, 200 mug, and 30 mg of E resulted in serum leve ls of E equivalent to those of pregnancy and were highly effective in preve nting mammary cancer. E treatment (20 mug) did not result in pregnancy leve ls of E and was not effective in reducing the mammary cancer incidence. In another set of experiments, we determined the effect of different durations of E with or without progesterone treatments on mammary carcinogenesis. Th ese experiments indicate that a period as short as one-third the period of gestation is sufficient to induce protection against mammary carcinogenesis . The pioneering aspect of our study in contrast to long-term estrogen expo sure, which is thought to increase the risk of breast cancer, is that short -term sustained treatments with pregnancy levels of E can induce protection against frank mammary cancer.