Cancer Stem Cells

Posted in: Blog | March 24, 2015

Cancer Stem Cells: are they the seeds that form the root of the problem in cancer patients who suffer a relapse?

There is a theory amongst doctors and researchers that has divided the field of cancer treatment in recent years.  It suggests the presence within a tumour of a small group of special cancer “seed cells” that are able to resist chemotherapy and bring about the return of the cancer many months after completion of treatment. The theory may explain the unfortunate relapses seen with many cancer suffers and the tragic consequences for the patient and their family.

 

These cancer seed cells resemble so-called “stem cells” that normally renew our tissues and organs throughout our lives. We are used to hearing about stem cells as the saviour of modern medicine for the treatment of untreatable illnesses and to reverse the damage done by conditions such as stroke and spinal column injury. However, these cancer stem cells represent a potential problem for the successful treatment of malignant disease. In fact, if the stem cell hypothesis is correct, they represent the root of the disease, which must be completely removed to ensure that the cancer does not grow back.

 

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The image above illustrates how the cancer stem cell theory might explain the return of cancer in a patient that has undergone conventional cancer therapy. It also illustrates how cancer stem cell specific drugs may lead to more effective treatments that shrink the tumour. The yellow cell represents a chemotherapy resistant cancer stem cell. By Peter Znamenskiy (Own work) [Public domain], via Wikimedia Commons

 

Cancer stem cell theory suggests that conventional chemotherapy kills the majority of cancer cells but leaves the rare stem cells alive. These stem cells ultimately reseed the tumour, which results in the cancer returning within the patient.  If the theory is correct then it should be possible to treat cancers by only targeting cancer stem cells.  Rather than attacking all of the tumour cells at once, as is the case for traditional cancer therapy. This should result in the tumour slowly shrinking, since the stem cells will no longer be present to replenish cells that naturally die within the cancer. This may take some time and a faster approach might be to use a combination of targeted cancer stem cell drugs along with conventional chemotherapy. 

 

Cancer stem cell theory looks incredibly exciting as a target for the treatment of cancer and as an explanation for the clinical relapses often seen in patients with metastatic cancer following conventional cancer treatments.  We must however observe caution, as many scientists are sceptical about the very existence of these specialised stem cells within a cancer. Other researchers believe that even if cancer stem cells do exist in some form, targeting them will not bring about the spectacular cures that patients and families are hoping for. Thankfully, there are some supporters of the theory who are willing to be risk takers.  As a result a number of bioscience companies and universities are now committed to clinical trials for new drugs that specifically attack these cancer stem cells.

 

The challenge for the scientists and clinicians involved in these trials appears twofold: not only do they have to prove that these drugs can be effective in treating and preventing reoccurrence of a cancer, they also have to show unequivocally that cancer stem cells are a realty.

 

In the coming years a wealth of information will become available from the current batch of clinical trials, aimed at utilising targeted cancer stem cell therapeutics. It remains to be seen if the results obtained will be enough to convince the sceptics that these stem cells actually exist in a tumour. On the other hand, if the targeted treatments are successful in preventing the return of cancer cells in children, should we really worry about proving beyond all reasonable doubt that this theory is correct? Maybe not!

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