New model to investigate cancer stem cells developed by UCLA researchers

How exactly do cancer cells originate? For decades, scientists have debated this question, weighing in on two competing theories. One theory is founded on the idea that all tumor cells are the same and as such, each has the same capacity to divide and form new tumors. The second theory suggests that only a few select cells -- cancer stem cells -- have the power to form new tumors. Over the past ten years, scientists have successfully isolated a variety of cancer stem cells -- including leukemia, brain and breast cancer cells. The belief today is that eventually, scientists will be able to trace back all cancers to their stem cells.

However, it is difficult to find and target stem cells since only a small percentage of the cells in a tumor are stem cells. The cells can lay dormant - and because they are not actively dividing, they can survive chemotherapy and even the newest molecularly targeted treatments being used today. At some point, stem cells renew themselves and begin to differentiate, thereby creating a new tumor -- the reason why some people suffer recurrences after years of being cancer free.

Now researchers at UCLA's Jonsson Comprehensive Cancer Center have developed a unique model that allows them to further investigate the stems cells that many scientists believe to be at the root of all lung cancers. As Raj Batra, an associate professor of medicine and a Jonsson Cancer Center scientist explains, "Lung cancer is not a single disease, but a collection of sub-types with different characteristics. Some lung cancers are invasive and spread quickly throughout the body, while some become drug-resistant."

Because stem cells possess unique properties, Batra proposed extracting candidate cancer stem cells directly from clinical specimens based on the markers they express and then validating their functionality. To locate the lung cancer stem cells, the team took specimens from patients suffering from malignant pleural effusions. This is a condition in which an abnormal amount of fluid collects between the thin layers of tissue lining the outside of the lung and the wall of the chest cavity. Their goal was to grow cells in a similar environment -- in the fluid from the pleural effusions -- that facilitates tumor growth within the body.

As noted in the study, which was published in the June issue of PLos One, "We were able to establish cultures in vitro with high efficiency using the novel strategy that utilized an autologous tumor microenvironment." As Batra explains, "We used not just the tumor cells but also the cells that accompany the tumor cells and the fluid they are living and growing in. This will allow us to develop a more representative model of lung cancer allow us to test, in patient specimens, which markers indicate the presence of lung cancer stem cells. Our ultimate goal is to define lung cancer and the cells that cause it so we can develop more effective therapies."

News Release: UCLA cancer researchers develop model that may help identify cancer stem cells  www.eurekalert.org   June 15, 2009

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