The mechanism of how cancer stem cells survive has been identified by a research team at Keck School of Medicine. This finding may one day lead to new therapies for a type of cancer with the highest incidence rates in the United States--Liver cancer.
"Liver cancer is difficult to treat, and most patients who are diagnosed with it will die within a five-year period," said Jing-Hsiung James Ou, senior author of a new study and a professor of molecular microbiology and immunology at the Keck School of Medicine. "My team has identified how liver cancer stem cells are maintained. Without these 'seeds of cancer,' liver tumors would shrink and eventually disappear."
New liver cancer cases went up 38 percent from 2003 to 2012, according to the Centers for Disease Control and Prevention. The disease's death rate increased by 56 percent to 23,000 deaths between 2012 and 2003.
A way to sidestep disease resistance
Liver cancer is resistant to most chemotherapy drugs. Only three drugs have been effective in shrinking liver tumors, but tumors become resistant to the treatment quickly, according to the American Cancer Society.
Ou and his colleagues found that mitophagy, the removal of damaged mitochondria (the cell's energizer batteries), is a potential therapeutic target. Mitophagy can cause tumors to proliferate. That is because a powerful tumor suppressor called p53 attaches itself to mitochondria. Removing mitochondria inadvertently removes the body's natural ability to keep tumors at bay.
If a lot of damaged "batteries" are removed, then the tumor suppressor p53 will also be removed: More cancer stem cells will be created, resulting in more malignant tumors. However, if this cell cleaning process is temporarily halted, then the number of cancer stem cells will diminish. Without these seeds of cancer, tumors will regress until they no longer exist, Ou said.
"Now that we understand the molecular process, we will be able to target this pathway to stop the production of cancer stem cells," Ou said. "If cancer stem cells are gone, cancer is gone."