Monday, 7 January 2013

Scientists create virus that kills CD133 positive cancer stem cells

A few days ago, scientists at the Paul-Ehrlich-Institut announced that they have successfully created an oncolytic virus that attacks and kills cancer stem cells that are CD133-positive. CD133 is a protein found in many different tumour-promoting stem cells. The study is very promising as the new virus showed equal, and in some cases superior, anti-cancer activity to the currently available oncolytic viruses.

Among other, tumours also contain cancer stem cells (CSCs). Cancer stem cells usually respond very poorly to chemotherapy and radiation and this is why there is always a high chance of cancer recurrence. Cancer stem cells are also the main culprit behind cancer metastasis. This is why a lot of researchers try to find new ways for identifying, attacking and killing them more efficiently.

Recent studies have shown that the CD133 protein is commonly found on the surface of many cancer stem cells. The PEI research group, led by Professor Christian Buchholz, and in collaboration with Heidelberg University and the German Cancer Research Center decided to take advantage of this protein and to use it against CSCs. To do so, they created a modified measles virus that uses the CD133 protein as a receptor to attach and penetrate CD133-positive CSCs. They then tested the virus on a mouse model and found that it is effective in the following types of cancer:
  • Glioma
  • Colon carcinoma
  • Liver cancer 
Picture of a measles virus of the genus Morbillivirus

In all of the experiments the virus showed great anti-tumoural efficacy and either eradicated the cancers completely or greatly suppressed and reduced them. Anti-cancer viruses aren't a new invention. But unlike the CD133 virus that attacks only cancer stem cells, the currently available anticancer viruses are non specific, attacking all the cells found within a tumour. So the scientists continued their tests to see how their virus compared to an oncolytic virus which is currently under clinical trials. Professor Buchholz said:

 "We were surprised that the CD133-specific virus showed an anti-tumoural activity which was at least as good as that of the standard virus. In the liver cancer model, the anti-tumoural activity was clearly superior and led to complete tumour remission"

It should be mentioned that the CD133 protein is also present on the surface of Hematopoietic stem cells (HSCs). But during the study, the HSCs  remained unaffected by the CD133 virus. This is due to the fact that hematopoietic stem cells have a natural resistance against measles viruses.

Video about oncolytic viruses

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