Vascular endothelia growth factor, and this is a growth factor which starts a cascade of gene expression to develop the vasculature in most of eukaryotes. It's the, like many of eukaryotic genes, it's spliced, there are six spliced isoforms of which three are pretty important. And so, one of the thing that has been done by many people, or tried by many people is to switch off VEGF in certain cancers because the tumours recruit blood vessels and they use VEGF, they also use other growth factors, FG, FBGF and so on, and so in the Sangamo lab they switched off the VEGF, in a number of cases, but I don't think it's reached therapeutic applications. The other thing we did here with Monika Papworth was to inhibit virus expression of herpes simplex virus, that was done here, using just six fingers. You needed six fingers to do it on rather than three fingers and we used our libraries. This is herpes simplex virus and we chose that deliberately because it's a very, highly infective. It carries with it its own VP16s, are activation they use in the virus particle and it carries six immediate early genes. And all of these, these genes interact with each other and there's a second set of genes which is the early genes, these are the immediate early genes, so as a kind of exercise we switched on, we decided to target a gene called 175K which is the most important of the immediate early genes. And using six fingers, using three fingers we were only able to reduce the infective titre by a factor of 20% but by six fingers we were able to reduce it by 90%, a ten-fold reduction, so that wouldn't be enough to... so if you wanted to use it as a therapeutic for virus you'd really have to target all the other immediate early genes. So you have to target at a very early stage because then by the time the virus starts replicating it's making more and more virus and you haven't got a hope. That's why we target the immediate early genes.

And we did the same, or rather I say we did, this time it was done by Yen Choo and Lindsey Reynolds at... Gendaq and they targeted HIV. And this was the, we made a lot of zinc finger constructs, partly they were made here, partly at Gendeq and you simply looked at the HIV promoter region and what you do, since we have now... zinc finger production is automated, high throughput automation, and they're cheap to make, you don't worry too much about looking for accessible regions in chromatin, which people did, what Sangamo used to do. It's like scatter bombing, you simply scatter enough zinc fingers around and you hope that some of them will be able to get through the chromatin structure. There was a lot of fuss made about determining chromatin structure. A man called Alan Wolffe, one of the leading people in the field who died unfortunately, advocated this, but it's not necessary. Because the promoters may be 300-bases long and you could usually find some way through. In fact, we found that you could switch off HIV expression in HeLa cells with the three-finger peptide. This surprised me no end until I discovered something about the life cycle of HIV. When HIV enters the cell, it picks up very cellular transcription factors including something called SP1, which is a three-zinc finger, a well-known three-zinc finger transcription factor, it uses the cellular factors. And by sheer chance, because we were simply doing, as I say, scatter targeting, this zinc finger we'd chosen bound the... obviously prevented the SP1 binding which meant that the other domain, the non-DNA binding domain of SP1 couldn't be put into play. So it stopped, actually, gave a pretty good result. And so we did things of this sort. So I think I decided that we could do more of these things, but we'd got enough proofs of principle and I think for virus diseases, anyway, you might use other targets, either vaccines or else small molecules and so on. So the... that's why I switched on to mitochondria.