Researchers Discover Effective Method For Killing Prostate Cancer Cells

By blocking a protein key to prostate cancer cell growth, researchers at the Lombardi Cancer Center at Georgetown University have discovered a way to trigger extensive prostate cancer cell death. This finding opens a new window for developing targeted treatments aimed at destroying prostate cancer cells before they have the opportunity to grow or spread. The study is published in the April 29 online issue of the Journal of Biological Chemistry.

“By preventing the Stat5 protein from being active, we were able to effectively kill human prostate cells,” said Marja Nevalainen, MD, PhD, assistant professor of oncology at Georgetown University Medical Center. “It’s similar to using a weed killer — poison ivy cannot take over the backyard if we don’t allow the leaves to breathe. If we stop this protein, which in turn stops the growth of prostate cancer cells, we are one step closer to managing the spread and growth of cancer in the prostate.”

Recent understanding of the correlation between prolactin, a hormone produced by male and female pituitary glands, and how it promotes growth of cells in the prostate led to this new study. Pioneering work by Dr. Nevalainen and colleagues established that prolactin serves as a local growth factor for prostate cells and that Stat5 is the specific signaling device for prolactin in prostate cells. In other words, Stat5 acts as an internal signaling device within the cell, receiving and sending messages of prolactin to the cell’s DNA.

In the new study, Nevalainen explored what happens if the activation of Stat5 in prostate cancer cells is blocked. Using human prostate cancer cell lines and viral gene delivery of an inhibitory mutant of Stat5, Nevalainen and her colleagues found that blocking the activity of this protein in prostate cancer cells will trigger extensive cell death.

“Once prostate cancer has metastasized, or spread, men have few treatment options other than chemotherapy and radiation,” said Nevalainen. “This finding could certainly lead to the development of new targeted therapeutics that can put the brakes on the growth of prostate cancer cells, allowing us to kill tumor cells, reduce the volume of tumors, and kill already metastasized cells.”

This study was funded by the National Cancer Institute (NCI).

Prostate cancer is the second leading cause of cancer death in men, exceeded only by lung cancer. According to the American Cancer Society, prostate cancer is the most common type of cancer found in American men, other than skin cancer. The ACS estimates that there will be about 220,900 new cases of prostate cancer in the United States in the year 2003. About 28,900 men will die of this disease. African-American men are disproportionately affected by the disease.