Researchers say these drugs leave ordinary cells unharmed

Researchers have discovered a way to identify drugs that can specifically attack and kill cancer stem cells, a finding that could lead to a new generation of anti-cancer medicines and a new strategy of treatment.

Many researchers believe that tumour growth is driven by cancerous stem cells that, for reasons not yet understood, are highly resistant to standard treatments. Chemotherapy agents may kill off 99 per cent of the cells in a tumour, but the stem cells that remain can make the cancer recur, the theory holds, or spread to other tissues in the body to cause new cancers. Stem cells, unlike mature cells, can constantly renew themselves and are thought to be the source of cancers when, through mutations in their DNA, they throw off their natural restraints.

A practical test of this theory has been difficult because cancer stem cells are hard to recognise and have so far proved elusive targets. But a team at the Broad Institute, a Harvard-MIT collaborative for genomics research, has devised a way of screening for drugs that attack cancer stem cells but leave ordinary cells unharmed.

Cancer stem cells are hard to maintain in sufficient numbers, but the Broad Institute team devised a genetic manipulation to keep breast cancer stem cells trapped in the stem cell state.

The team, led by Dr. Piyush B. Gupta, screened some 16,000 chemicals, including all known chemotherapeutic agents approved by the Food and Drug Administration. The team reported in the Thursday issue of Cell that 32 of the chemicals selectively went after cancer stem cells. These particular chemicals may or may not make good drugs, but the screening system proves for the first time, the researchers say, that it is possible to single out cancer stem cells with drugs that leave ordinary cells alone. Only one of the 32 chemicals is approved as a drug for cancer. — © 2009 The New York Times News Service