March 1, 2012 | by City of Hope Staff
The stem cell we’re most familiar with is the friendly version that may eventually help us treat brain tumors or cure macular degeneration. Stem cells can make copies of themselves almost forever, and those copies can either continue the duplication or turn into specific new cells that replace old, worn-out ones. It’s one way the body repairs itself.
Cancer cells can copy themselves almost forever, too. But unlike good stem cells, they steal resources from the healthy cells around them to continue growing out of control. Many researchers think that cancers have stem cells of their own that exist to only make more cancer cells.
Leukemia, for one, has cancer stem cells that can survive most chemotherapy and radiation treatments. These leukemia stem cells hide away in safe pockets in the bone marrow to build up a new swarm of leukemia cells that can start the cancer all over again. Patients with chronic myelogenous leukemia (CML) can take drugs for years to suppress these cancer cells, but the treatment often comes with heavy side effects. And sometimes leukemia grows immune to the drugs.
The best hope for a cure without years of drug treatment is killing off those hardy leukemia stem cells.
Ravi Bhatia, M.D., director of the Division of Hematopoietic Stem Cell and Leukemia Research, WenYong Chen , Ph.D., assistant professor of biology, and research fellow Ling Li , Ph.D., discovered a key defense mechanism that helps the leukemia stem cells stay so invincible. They published their findings in the journal Cancer Cell.
The team found that CML cells pump out a huge amount of a protein known as SIRT1. This is where leukemia stem cells get crafty. SIRT1 likes to turn off a gene known as p53, which acts as a security guard for the body against cancer. Normally, when the DNA in a cell is damaged — whether it was simply worn down or harmed by toxins — the p53 gene gets turned on to eliminate the potentially cancer-causing problem: It makes the faulty cell kill itself.
When the researchers cut off SIRT1 in the lab, p53 came roaring back and took out the leukemia stem cells. City of Hope scientists aim to turn those findings into a therapy that tackles CML at its source.