Saturday, 28 August 2010

Viruses vs Cancer!

A paper published in Clinical Cancer Research earlier this month describes a treatment for cancer that utilises the herpes simplex virus to selectively kill cancer cells, while leaving normal human cells intact due to deletions that make it unable to grow in them. I'm almost certain this is the same treatment I heard about in a lecturer's anecdote in first year (obviously quite a way before the study was published):

This group had developed a treatment for cancers of the head and neck, using the herpes virus. The treatment is pretty effective at shrinking tumours and making surgical removal of the remaining tumour possible. They have one patient with a tumour on his tongue, which understandably limits his diet - he probably has to be fed through a tube. So they use this treatment on him, the tumour shrinks, they operate, he's discharged. A few months later, though, he's back - with liver failure.



A side effect of the new treatment? Nope - he was so excited about being able to eat and drink properly that he'd been getting plastered constantly, and ruined his liver!

I have no idea how true that anecdote may be, but it amused me, and it does serve to show how people can react to what might be perceived as a 'miracle cure'. Virus-mediated attack on cancerous cells does seem, at first glance, to be something of a miracle cure. It's the perfect solution, really - viruses have evolved to invade and kill cells. The trick is to get them to do so selectively, so as to not cause further damage to a patient.

In this case that is done by certain deletions, one of which prevents the virus replicating in non-tumour cells, while the other would usually prevent antigen presentation, allowing the virus to evade the immune system. The virus also contain a copy of the human granulocyte/macrophage colony-stimulating factor (GM-CSF), which stimulates production of white blood cells. This produces a virus that: replicates only in tumour cells; lyses tumour cells; stimulates the immune system to attack those tumour cells.

This study looked at treatment with the virus, at various dosages, in combination with chemoradiotherapy. The sample size was just 17, and there was no control group, which does make the results sound rather dubious, but the main purpose of the study was to suggest an appropriate dosage and treatment schedule for further trials, not to show effectiveness. Nevertheless, some dosage dependent effects were seen, suggesting that the virus is effective against tumour cells. It has also previously been shown to be effective (and safe) in mice.

I'm looking forward to seeing how this trestment performs in larger scale trials. Harnessing viruses to kill cancer cells is a pretty cool idea, and this could be a very useful addition to the medical arsenal of cancer treatments.  I believe I've also read somewhere about using bacteriophage to attach bacterial infections - but that will have to wait for another time.

References:


Harrington et al, Phase I/II Study of Oncolytic HSVGM-CSF in Combination with Radiotherapy and Cisplatin in Untreated Stage III/IV Squamous Cell Cancer of the Head and Neck, Clin Cancer Res; 16(15) August 1, 2010


Liu et al, ICP34.5 deleted herpes simplex virus with enhanced oncolytic, immune stimulating, and anti-tumour properties, Gene Therapy (2003) 10

2 comments:

  1. Phages are amazing little things, I did some work on them for my first every summer project and they seemed to have a lot of potential for antibacterials. Unfortunately most of the research (apart from more modern things) seems to have been carried out somewhere in Russia in less than optimal scientific conditions, so it's not all written up particularly well.

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