Breast
Hormone Decreases Ability of Breast Cancer to Spread
By Journal of the National Cancer Institute
May 4, 2005, 17:26

A hormone used in the contraceptive Depo-Provera increased expression of a metastasis suppressor gene and decreased the ability of breast cancer cells to spread in both laboratory experiments and an animal model.

Medroxyprogesterone acetate (MPA) is a progestin that is used in Depo-Provera and has been tested as a treatment for advanced breast cancer. An earlier study found that MPA increases the expression of a metastasis suppressor gene called Nm23-H1 in estrogen and progesterone receptor-negative breast cancer cells via the glucocorticoid receptor. Patricia S. Steeg, Ph.D., of the National Cancer Institute, and colleagues tested whether treating hormone receptor�negative breast cancer cells with MPA could decrease the ability of the cancer cells to metastasize.

In cell line studies, the authors found that MPA treatment reduced the colony-forming ability of human breast cancer cells and that it did so via its effect on Nm23-H1. In animal studies, mice with breast cancer micrometastases were randomly assigned to injection with MPA or a control substance. Mice injected with MPA developed fewer and smaller lung metastases than mice injected with the control.

In an editorial, V. Craig Jordan, Ph.D., D.Sc., of Fox Chase Cancer Center in Philadelphia, suggests that the novel mechanism targeted in this study may be exploited in the future treatment of estrogen receptor�negative breast cancer patients. He also notes the clinical challenge of preventing metastasis in a disease that is typically diagnosed after metastatic spread has already occurred.

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