March/April 2006

First Lung Stem Cells Discovered

May lead to the early detection of lung cancer

By Tracy Staedter

Scientists at MIT's Center for Cancer Research have discovered stem cells -- cells that do not yet have a specific function -- in the lung. Not only is this the first time anyone has found stem cells in the lung, but the team claims that these cells could be the precursor for lung cancer, the cancer that causes the greatest number of deaths in the U.S. each year. In the future, locating the cells could be a new approach to identifying the disease at its earliest stage.

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"We think those cells are the ones that first proliferate after a [cancer] gene gets activated," says Carla Bender Kim, a postdoctoral fellow at the center and lead author of the study, which was published in the journal Cell.

According to Bender Kim, only 2 percent of people diagnosed with advanced-stage lung cancer survive, but the survival rate jumps to 50 percent when the disease is caught much earlier. "If we could use this knowledge of stem cells to learn more about the human situation, that would be very helpful," she says.

Bender Kim and her team identified the stem cells in the region of the lungs between the airways -- or bronchioles -- and the place where carbon dioxide in blood cells is exchanged for oxygen -- known as the alveoli. She named the group bronchioalveolar stem cells.

In tests conducted in culture dishes and on mice genetically engineered to develop a form of lung cancer similar to one found in humans, the team found that these bronchioalveolar stem cells were the first to divide and the only cells to increase in number once a mutant gene that initiates cancer was activated -- a good indication that they might be playing a significant role in the growth of the disease.

"If any DNA damage occurs that doesn't get repaired, those cells maintain that damage for a long time," says Bender Kim.

The findings could lead to new diagnostics and treatments. For example, molecular imaging methods could look for unusual activity in the bronchioalveolar cells. Researchers could develop a drug that attacks only the stem cells within a tumor and not other healthy cells nearby.

Although the findings are significant, they raise more questions, says Bender Kim, such as whether these stem cells are present in human cancerous tissue and what controls the cells in the first place. She'll be tackling those questions in the years to come.