"What we ended up doing was shifting our understanding of liver stem cells and their role in malignancy," Rountree said. "All work previously done was looking at patients, animal models or cell lines after the tumor already developed. What we did was identify malignant stem cells before there is evidence of the primary tumor. This gave us a new perspective on not only what the potential of stem cells for therapy is, but also in terms of what's driving cancer formation. Imagine treating a cancer before a primary malignancy forms."

Researchers created ten cell lines to study using a single-cell isolation technique. Cells that make a unique surface protein called CD133 were separated by placing them in a liquid medium and running through a flow cytometer. Once identified, a robot took a single CD133-positive cell and placed it in a single drop into one well of a culture dish. Doing this several hundred times, the cell lines were established.

These single cells, when expanded up, had stem cell characteristics, having markers of both hepatocytes and cholangiocytes. When these lines were injected into a mouse with a deficient immune system, the tumors then formed.

Rountree said there is interest in targeting these stem cells with malignant potential. "Can we target these cells in patients with hepatitis B or C, either before or after their cancer forms?" Rountree said. "The broader implication is very powerful. If you look at a patient with chronic injury and find a way to specifically target cells with malignant potential, you may be able to prevent liver cancer in the first place."

Source: Penn State Hershey Medical Center, Penn State College of Medicine