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flu-like symptoms, which is trivial compared to other forms of therapy. A larger follow-up study is already underway, and the virus is being tested on other types of cancer. Although that work involved injecting tumours directly, many of the same researchers have previously shown that JX-594 can be administered intravenously. In a trial published in 2011, a single infusion was shown to infect the tumours – without harming healthy tissue – of 23 people whose cancer had spread to several organs. This is crucial, not only because tumours anywhere in the body can be treated this way, but because tumours become virtually incurable by existing methods when they start spreading to other organs and tissues (something called metastasis). Viral therapy can be especially effective against such metastatic cancers, but blood-borne viruses are easily mopped up by antibodies, so avoiding the immune system until the virus has done its job is probably the biggest obstacle to developing a full-blown oncolytic cure for cancer. Metastasis is what ultimately kills most people with cancer, but scientists don’t completely understand how it happens. Epithelial tissue is one of four tissue types (the others being connective, nerve and muscle), and epithelial cells form the surface of many structures in the body, including the lungs, liver, and breasts. But epithelial cells bind together tightly in stable tissues – so researchers have been left puzzling over how their cancerous versions spread around the body. A paper published in Science this January, however, provided the best evidence yet supporting a strong theory of metastasis, namely that it involves something called “epithelial-mesenchymal transition”. Mesenchymal cells don’t bind to each other and can move more freely, so it was thought epithelial tumour cells

might become more like mesenchymal cells to enable them to enter the bloodstream and circulate. There was some support for this theory from animal studies, but researchers in the recent study tracked and genetically analysed circulating tumour cells (CTCs) in 11 women with breast cancer. They found that when the tumours were responding to chemotherapy, the proportion of CTCs with mesenchymal properties fell, but rose when therapy failed. Many had features of both epithelial and mesenchymal cells, however, suggesting the real enemy may be an intermediate cell type. The work paves the way for researchers to more easily track how cancer spreads, and could provide a range of new targets for drug developers. Other attempts to tackle this problem include using reovirus - a naturally occurring oncolytic that “piggybacks” on blood cells so as not to be attacked by the immune system, and a study which hid an engineered adenovirus inside white blood cells to deliver it to a prostate cancer in mice. Excitingly, this technique uses the immune system itself – spurred into action by chemotherapy or radiotherapy – to deliver a viral payload which “completely eradicates” tumours, but it is yet to be tested in humans. Watch this space…

PA G E 1 9 • A P R I L / M AY 2 0 1 3 • I S S U E 1 1 • G U R U

(X-ray) Wikimedia • Lange 123, (Vaccine) Flickr • AJC1

Guru Magazine Issue 11: They're watching you.  

A unique FREE bi-monthly mag for the thinking person. Entertainment, news and science - but there aren't any lab goggles in sight. Inside t...

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