Cancer cells spread by releasing 'bubbles', according to an ...( This release is available in A HREF h...),Health

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Montreal, April 21, 2008 A new fundamental mechanism of how tumour cells communicate has just been discovered by the team of Dr. Janusz Rak at the Research Institute of the McGill University Health Centre (MUHC) in collaboration with Dr Guha from the University of Toronto. The cancer cells are able to communicate with their more healthy counter-parts by releasing vesicles. These bubble-like structures contain cancer-causing (oncogenic) proteins that can trigger specific mechanisms when they merge into non or less-malignant cells. These findings could change our view on how cancerous tissues work and lead to major clinical innovations. They were published on April 20 in the on-line edition of Nature Cell Biology.

The surface of some brain tumour cells has long been known to express a mutated version of what is called the variant III epidermal growth factor receptor (EGFRvIII). Although this factor is expressed only in a fraction of tumour cells, it has a major impact on the malignancy of the whole tumor. How could this cellular minority have such an important impact" This mechanism was still unknown until now.

This study shows that the mutated EGFRvIII triggers production of small vesicles that project from the cell membrane and that carry mutated copies of EGFRvIII on their surfaces. They were baptised oncosomes. Surprisingly enough, this shows that oncoproteins are not always confined to the cell that produced them. In this case they even migrate!

Oncosomes will migrate until they fuse with another cell, either healthy or benign tumoral. Oncogenic protein AGFRvIII then becomes integrated in the membrane of the recipient cell and starts stimulating specific metabolic pathways to make it act in an aberrant and malignant way. Although this may be a transient event, the changes could impact tumo
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