Two new studies conducted by Canadian and Italian Scientists have found that
cancer stem cells may be the source of colon cancer. Scientists made the discovery when human colon cancer stem cells, which were implanted in mice, appeared to initiate colon cancer tumors.
Although previous studies have already shown that cancer stem cells may be responsible for breast cancer, brain cancer and leukemia, these latest findings are the foremost to show that cancer stem cells may also be responsible for the occurrence of colon cancer. Their findings may help future cancer treatments to target more on cancer stem cells to try and prevent its reoccurrence.
Stem cells are immature cells which have the capacity to differentiate into any specialized cell types. Cancer stem cells share many characteristics of stem cells such as the capacity for self renewing cell division. However, although stem cells have the ability of dividing only when there are specific conditions, the cancer stem cells do not have such controls.
Dr. John Dick, senior scientist at the Ontario Cancer Institute, Princess Margaret Hospital, Toronto, who was the principal investigator for the research, said "We found that not every tumour cell is equally capable of sustaining tumours in the colon.
Colon cancer stem cells are the driving force initiating and sustaining these tumours. Since this is the heart of the tumour, you have to find and kill each of these colon cancer stem cells
to truly cure the disease."
He along with his colleagues conducted the research on laboratory mice that were immune deficient, which means they do not have the
disease fighting cells and thus the cancer growth is not hampered.
The research team took samples of tumours from humans in whom the cancer had spread, and broke down these tumours until they had individual cells. Millions of these individual cells were then implanted in laboratory mice. The researchers found that only those cells which had the presence of CD133, which is a protein on the surface of cells, had the ability to initiate new tumours.
In another study which was conducted in Rome, Ruggero De Maria of the Istituto Superiore di Sanita, along with colleagues also found that these same CD133 cells when implanted in immune deficient mice, were able to start tumours.
"Now we know that we can get human tumours growing in an animal and the tumour looks identical to the tumour that's growing in a patient," said Dr. John Dick. "What we showed was we basically never got a tumour when we transplanted the CD133-negative cells. And all of the mice that were transplanted with CD133-positive cells gave us tumours. Everybody understands that if you get colon cancer, the big risk is that it could come back. Cancer can relapse and colon cancer regrettably is one of those cancers that has a high rate of relapse. So it could be that the chemotherapy that we're using today is not targeting these cancer stem cells properly. And it's these cancer stem cells, because they're not targeted, they survive the chemotherapy," he added.
The researchers said in their report: "Colon cancer is one of the best-understood neoplasms (tumors) from a genetic perspective, yet it remains the second most common cause of cancer-related death (in Canada), indicating that some of its cancer cells are not eradicated by current therapies."
The findings of these studies have been published on Sunday in the journal Nature in their advance online edition.
