|Breast Cancer Stem Cells May be Key to Multi-drug Resistance|
When breast cancer stops responding to drugs, stem cells might be the cause of it. A study that catalogues breast cancer stem cells is identifying the mechanisms of resistance to develop treatments.
Crane: Multi-drug resistance occurs when cancer cells in tumors no longer respond to drugs.
Gottesman: The basis for that resistance is a residual group of cells within the tumor that have been called cancer stem cells.
Crane: Dr. Michael Gottesman is the director of the Clinical Research Center at the National Cancer Institute. He is the principal investigator of a study that examines breast cancer stem cells.
Gottesman: But our original idea was to look at those cells and ask whether they expressed some of the markers associated with drug resistance, and indeed they do. Crane: The study has examined hundreds of cancer cells and identified nearly four hundred causes of drug resistance.
Gottesman: Our general approach is to try to catalog all the ways in which cancer cells can become resistant to anti-cancer drugs, and then determine in clinical samples, either on a personal basis, that is for each tumor that comes to the attention of a pathologist, which genes are expressed and which are not expressed, and then develop cocktails of treatments that can circumvent that resistance; or find certain themes that are common for most cancers, and that can lead to new ways of treating cancer.
Crane: Dr. Gottesman says the key is catching cancer early enough so that the diseased cells donít spread and develop mechanisms to resist the drugs.
Gottesman: One of the problems with most patients who come to the doctor is the cancer is quite large, or has spread, and there are many, many cells. And the more cells you have the more likely that one or more will develop a resistance mechanism. So if you can get tumors when they are relatively small or not metastasized, then you are more likely, I think, to be successful with chemotherapy.
Crane: Dr. Gottesman says the findings may lead to new drugs based on common mechanisms of resistance, or pave the pathway to personalized therapies. For more information go to www.cancer.gov. This is Kristine Crane at the National Institutes of Health, Bethesda, Maryland.