Researchers at the University of Maryland Greenebaum Cancer Center have made a discovery that may explain why some cases of breast cancer and other forms of cancer are resistant to chemotherapy. Their findings, published in the December 22, 1998, issue of Proceedings of the National Academy of Sciences, may lead to better ways to target chemotherapy to individual patients and may open the door to new strategies to reverse resistance to cancer-fighting drugs.
"We have found a cancer resistance protein that rapidly pumps out chemotherapy from a certain line of breast cancer cells," says L. Austin Doyle, M.D., associate professor of medicine at the University of Maryland School of Medicine who is the lead author of the article.
The researchers call the newly-discovered pump Breast Cancer Resistance Protein (BCRP). They found that this protein pumped three common anti-cancer drugs out of cells rapidly, before the drugs could get to the nucleus of the cancer cells and destroy them.
"This is only the fourth molecular drug resistance pump of anti-cancer drugs to be identified, and it is half the size of the other pumps," says Douglas D. Ross, M.D., Ph.D, professor of medicine at the University of Maryland School of Medicine. "We had been looking for years for a way to explain resistance among this group of resistant cancer cells, so this is an important step," adds Dr. Ross, who is a co-author of the article.
The researchers, along with Lynne Abrusso, M.D., Ph.D, assistant professor of pathology at the University of Maryland School of Medicine, studied resistant and non-resistant cancer cells to find genes that were different among the two groups. They used molecular biology techniques to isolate the unique BCRP gene from drug-resistant cancer cells. Then, they tested their theory by changing non-resistant cells into resistant ones by inserting the BCRP gene into them.