The Role of Prolactin in Breast Cancer

This finding, published in the May 14, 2002, issue of the Proceedings of the National Academy of Sciences, somewhat contradicts the established view that protein hormones act through receptors on the surface of the cell.

"Traditionally, it was thought that protein hormones, like prolactin, only work on the outside of cells as if their only job was just to hit the ‘on' switch,” said Dr. Charles V. Clevenger, assistant professor in the department of pathology and laboratory medicine at of University of Pennsylvania (Philadelphia, USA).

Prolactin is necessary for the production of breast milk. Its role in stimulating the growth of breast cancer has been only recently recognized, and recent studies have found that human breast cancer cells produce prolactin. Elevated prolactin levels in the blood significantly increase the risk of developing breast cancer.

As prolactin requires interaction with cyclophilin B to enter cells, researchers used modified forms of cyclophilin B to prevent this from happening. They found that by removing the peptidyl-prolyl isomerase activity of cyclophilin B, the entry of prolactin into cells could be blocked with the resulting inhibition of breast cancer development.

This research helps to chart a new pathway through which hormones work and spotlights new opportunities for targeted drug development.



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