Discovery of how prolactin travels to gene's machinery helps explain role.

2003 MAY 8 - (NewsRx.com & NewsRx.net) -- Prolactin, a naturally occurring peptide hormone needed for milk production following pregnancy, has been found to play a major role in the development and spread of breast cancer.

More recently, Dr. Charles Clevenger, the same researcher who first demonstrated the scope and mechanism of prolactin's role in cancer, has discovered that prolactin functions directly inside the cell, not merely by sending signals across the cell membrane as had been assumed for it and all other peptide hormones.

Clevenger also has discovered how prolactin is able to travel across the cell membrane and directly into the DNA machinery of the cell. These findings suggest a pathway through which new therapies could block the growth and spread of breast cancer - and offer a new paradigm for how other hormones function, not just in breast cancer but in a number of other diseases.

The University of Pennsylvania researcher described his research at the Experimental Biology 2003 meetings in San Diego. He was honored by the American Society of Investigative Pathology, at the EB 2003 meeting, with the Pfizer Outstanding Investigator Award. The award honors a decade of steady unraveling, by Clevenger, of how prolactin works in breast cancer, including this most recent discovery.

Although scientists recognized prolactin was involved with breast cancer in rats as early as the 1970s, they focused solely on the hormone produced by the pituitary gland in the brain. Human trials based on this assumption failed miserably. But in the 1990s, using greatly improved technology and techniques, Clevenger was able to show that breast tissue itself produces prolactin in significant quantities and that more than 95% of all breast cancers express the prolactin receptor, meaning prolactin was active in the tumors. At the same time, a large population study of nurses had found that women with higher levels of prolactin were at greater risk for breast cancer.

Soon thereafter, Clevenger was able to show how prolactin organized the breast cancer cells to move from the breast to other parts of the body.

His most recent discovery is how prolactin is able to get to the DNA of the cell and what it does there. For years, scientists assumed that as a peptide protein, prolactin worked from a distance, outside the cell (unlike steroid ...