PARIS - Researchers at the Institut Curie and the Institut Gustave Roussy (IGR) have discovered a new vector for administering an antitumor vaccination.

The vector consists of exosomes secreted by dendritic cells, which express class I and II CMH (complex major histocompatibility) molecules and can thus specifically stimulate T lymphocytes. Using them as an antitumor vaccination entailed producing exosomes from dendritic cells that previously had been exposed to tumor fragments (peptides).

When this vector containing a fragment of tumoral antigen was injected into mice with cancer, the tumor either shrank or disappeared altogether. The result demonstrated that the part of the immune system stimulated by these exosomes specifically attacked cancerous cells and did so very effectively.

The researchers, led by Sebastian Amigorena of the Institut Curie, in Paris, and Laurence Zitvogel of the IGR, in Villejuif, near Paris, think these dendritic exosomes, which are a sort of natural liposome, are a new agent in the communication between cells of the immune system. They argue that, compared with tests under way with dendritic cells themselves, a cancer immunotherapy based on the use of dendritic cell-derived exosomes could prove easier to control and yield better results.

They are now testing this new form of immunotherapy in the prevention of tumor relapses caused by cancerous cells that have survived earlier therapy (whether it be surgery, chemotherapy or radiotherapy). Their theory is that, since the organism already knows the tumor, if it is shown it again through the intermediary of exosomes, it should be able to react more rapidly and more effectively. - James Etheridge

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