Science Questions

Could viruses be engineered to attack cancer cells selectively?

Chris -  They have been.  This is a really hot area because viruses are very bad for cells.  They basically turn cells into virus factories.  They will go into the cell.  They will grow very fast in the cell, turning it into a virus factory and kill the cell in the process.  Researchers are thinking if we can exploit that then we might have a way of making the virus attack just a cancer and kill it.  There have been a number of approaches to doing this.  Up in Scotland Moira Brown who’s been on this programme has been working on a strain of Herpes Simplex virus, the virus that causes cold sores, for example.  She’s found a mutant form of the virus which has damage to a gene called gamma 34.5 and this gene, if you switch it off, stops the virus growing in brain tissue.  What this means is that if you have a brain tumour you could inject the cancer with this virus.  Because the brain tumour is very fast growing cells the virus can still grow in those cells.  It will replicate making more virus which will go into more cancer cells and kill those cells which will go into more cancer cells.  The whole thing grows until it runs out of cancer cells.  As soon as it hits the healthy tissue interface where the healthy brain tissue is again it switches off.  This is viewed as a very powerful way to very selectively weed out the tumour cells that are growing invasively between the healthy tissue without actually having to do radical damage with a scalpel to someone’s brain.

Dave - Would you have to have a different virus for each kind of cancer or would you be able to get one which would get the most?

Chris - Not necessarily but the likelihood is there’s going to be horses for courses.  Some viruses naturally have a tropism, a tendency to go into certain cells types.  HIV for example, tends to home in on white blood cells.  If you wanted to target a certain kind of disease of those white blood cells you might use a virus to start with which is very good at homing in on certain types of tissue.  Other times it’s been a case of modifying the virus so that the receptors or docking stations on the surface of the cell are slightly different so that they will then go onto certain types of cells.  It’s a work in progress, isn’t it?

Kat -  There’s lots of research that’s going on funded by Cancer Research UK.  Ovarian cancer is a cancer that’s really ripe for virus treatment because mostly ovarian cancer tends to stay inside the tummy, in the same place.  You can kind of inject the virus in there and it will get rid of all the cancer cells.  There’s some clinical trials that are currently underway.

September 2008