Researchers from Toronto, Canada have found that only a small portion of a tumor is responsible for spreading cancer and not all the cells as believed earlier. //
This is the fourth type of cancer in which stem cells have been found to be the source of the disease. Previously it was discovered in leukaemia, breast and brain cancers. This finding supports the view - stem cells may be responsible for all cancers.
This study will definitely help to find more effective treatment options according to the author John Dick, who is a senior scientist at University Health Network and also a professor of molecular and medical genetics at the University of Toronto.
Treating cancer stem cells alone will be a better way of dealing with the disease, says Dick. He compares cancer with a backyard weed. "You can keep cutting the leaves off the weed, but the weed will regrow," he explains. 'But if you cut the tap roots, the leaves will wither away. Killing the cancer stem cells is the equivalent of killing the root of the weed.'
Dick identified cancer stem cells in a type of leukemia ten years ago. Since then other researchers have discovered stem cells responsible in breast tumours. Two years ago, Peter Dirks, assistant professor in the University of Toronto's department of surgery discovered stem cells in brain tumours.
"This is a really important additional discovery in a really important human cancer," says Dirks, also a scientist at the Hospital for Sick Children.
In this research , human colon cancer cells were implanted into mice which degenerated immune systems. The researchers found that a small number of cells, which had a protein called CD133 on their surface, were active in spreading and maintaining cancer.
Their findings were published in the journal Nature.In the same issue of Nature, a group of Italian researchers also have announced a similar discovery .
In the second stud
y, Ruggero De Maria of the Istituto Superiore di Sanita in Rome and colleagues found the same CD133 cells started tumours when injected into immune-deficient mice.
These two studies are the first to show that cancer stem cells are responsible for colon tumours.
That two independent research groups identified colon cancer stem cells reveals the power of this hypothesis, Dirks says.
"The big challenge now is to learn how to target and kill these cells," he says,
“As other studies have shown that cancer stem cells in brain tumors are resistant to radiation and leukemic stem cells seem to be resistant to chemotherapy.”
To understand the molecular program of colon cancer stem cells seems to be their next step and also to find out if the cells have properties that make them resistant to chemotherapy. They hope to be funded by the new Ontario Institute of Cancer Research.
"Colon cancer is one of the most common forms of human cancer, but we don't know a lot about the genetics of how it starts," says Dick."It's important to try and understand these (cancer stem) cells."
Colon cancer is the fourth most dangerous cancer , killing 655,000 people every year, according to World Health Organisation.
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