Experts find rogue stem cells in liver cancer

Liver cancers are embedded with a type of super cancer stem cells that make them resistant to chemotherapy, spread to other body parts and stage a comeback even after they are surgically removed, researchers in Hong Kong reported on Thursday.

The discovery, published this week in the journal Cell Stem Cell, is important because it means experts can target these stem cells in their fight against liver cancer, a major blight in China and southeast Asia.

These cancer stem cells have a unique surface protein called CD24 and patients with high counts of CD24 tend to have poorer chances of survival, said lead researcher Irene Ng, pathology professor and director of the State Key Laboratory for Liver Research at the University of Hong Kong.

"CD24 is like a button, a switch on some cancer stem cells. Once they are switched on, they activate a protein in the cell called STAT3," Ng told a news conference.

Her colleague Terence Lee said: "STAT3 goes into the nucleus of the cells and carries out its functions, which are to form tumors, spread and be drug resistant. If we inhibit the function of STAT3, we block the function of cancer stem cells."

Stem cells are master cells found throughout the body and they are special because they can transform into different cell types and multiply and self-renew.

Liver cancer stem cells are therefore troublesome because they are responsible for growing tumors, making them spread, drug-resistant and so hardy that they recur even after they have been surgically removed.

In their experiment, Ng and colleagues found that mice that were implanted with liver cancer enriched with CD24 cancer stem cells were resistant to chemotherapy.

They then injected two colonies of liver cancer cells - one with CD24 stem cells and the other without - into separate parts of the liver of the same mouse.

"That part of the liver with CD24 cancer stem cells grew cancer and the cancer spread to the lungs. But not the other part of the liver without CD24 cancer stem cells," Lee said.

They went back to human liver cancer patients and found that those with high concentrations of CD24 had a 67 percent chance of cancer recurrence in the first year after surgery, compared to 21 percent recurrence in those with low CD24 count.

Those with high CD24 count had a 80 percent chance of their cancer spreading to other body parts, compared to 32 percent chance of spreading in patients with low D24 count.

Ten percent of China's population carry the hepatitis B virus, a key cause of liver cancer. There are 500,000 new cases of liver cancer worldwide a year, over 50 percent in China.

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By Tan Ee Lyn

HONG KONG