14 June 2012

Anti-cancer virus hitchhiking

The virus gives new hope for success in the fight against cancer

Roman Ivanov, Computer

Scientists have shown how a common respiratory intestinal virus destroys cancer cells, triggering an immune response, like a vaccine when injected into a patient's bloodstream. Thus, another important step has been taken in the development of new anti-cancer drugs.

Researchers from the University of Leeds and the Institute of Cancer Research (both in the UK) report that the ability of the reovirus to attach itself to red blood cells allows it to avoid attacks of antibodies in the bloodstream, which, otherwise, could neutralize its anti—cancer abilities. This makes it possible to inject the reovirus drug intravenously — as it is done with conventional chemotherapy treatment. Recall that other viral agents are attacked by the immune system, and therefore require direct injection into the tumor, which, in fact, nullifies the significance of this approach.

The uniqueness of reovirus as an anti-cancer drug does not end there. As it was shown during trials on ten patients with late-stage bowel cancer, the reovirus inflicts a double blow to cancer cells: firstly, infected cancer cells die from the direct action of the virus, and secondly, infection triggers an immune response that helps to finish off those cancer cells that remain alive.

But that's not all. In patients with colorectal cancer with liver metastases, it was confirmed that the reovirus affects only malignant cells, without touching healthy tissues. Ten patients who were waiting for an organ transplant were given a course of viral therapy a few weeks before the operation. When the cancer-stricken organs were removed and examined four weeks later, it turned out that the cancer cells had turned into factories for the production of active reovirus, while healthy liver tissues were completely unaffected.

Thus, a picture is emerging that cannot but encourage. Due to its ability to move around the body on the "back" of red blood cells, the reovirus is not destroyed by the immune system and can be injected intravenously. In this case, he is able to reach a tumor located anywhere in the body. The reovirus infects only cancer cells without affecting healthy ones, which guarantees against side effects. After infection, malignant cells actively produce new reoviruses, gradually dying. Finally, infection activates the immune system to fight infected and uninfected (at the same time!) cancer cells.

Illustration University of Leeds

It remains only to understand why only cancer cells are susceptible to a viral attack and why there is a response of the immune system. And the answer is simple: the malignant cells themselves are to blame. Their irrepressible desire to turn off all protective cellular mechanisms finally came out sideways to them. Healthy cells are reliably protected from infection by reoviruses with PKR protein (protein kinase R). And in many types of cancer cells, the Ras protein is activated, blocking PKR activity, which allows reoviruses to penetrate the tumor. Infection of cells leads to the fact that they begin to produce proteins that prevent inflammation, such as interferon-beta and interleukin-8, which, in turn, activate white blood cells (in particular, cytotoxic T cells), which is the cause of the immune system's attack on cancer cells infected with reovirus.

The results of the study (Adair et al., Cell Carriage, Delivery, and Selective Replication of an Oncolytic Virus in Tumor in Patients) are presented in the journal Science.

Prepared by the University of Leeds: ‘Hitch-hiking' viral therapy deals a double blow to cancer.

Portal "Eternal youth" http://vechnayamolodost.ru14.06.2012

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