Magnetic nanoparticles detect cancer

31 July 2018

Interview with

Sam Gambhir, Stanford University

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One of the reasons cancer is so often deadly is that it is usually caught relatively late, at a stage where treatment is less likely to be effective. This is because at present we don’t have a method that’s sensitive enough to detect early cancers reliably - standard scans and blood tests simply aren’t good enough. This is precisely the problem a team of researchers at Stanford University have set out to tackle - using a combination of nanoparticles and a tiny magnetic wire. To find out more, Isabelle Cochrane spoke to Sam Gambhir, Professor of Cancer Research at Stanford University…

Sam - We know that tumours shed different molecules that end up in the blood and the problem is that when the tumour is small and very early, the molecules that are being shed into the blood are present only in very low quantities. And so, to find these rare molecules from an early tumour we need a way in which we can go into your blood and filter out all those molecules.

The idea is that this little magnetic wire called Mag Wire, which is about a millimetre in diameter and about 6 millimetres in length. It’s made up of tiny little magnets, very powerful little magnets that can enter your body in the vein, and then if anything magnetic is going by, the magnets and the wire will attract those magnetic molecules that are going by. So we also put in little magnetic nanoparticles that stick to the molecules the tumour is making, so within about 20 minutes of having a wire in your blood we can sample the entire blood volume in your body, pull out the wire and then analyse everything stuck to it so that we can get a detailed assessment if there may be a hidden tumour.

Isabelle - How do you specifically manage to tag the tumour molecules themselves rather than anything else that’s floating around in the blood?

Sam - We can target anything we want in the blood by using the properly of antibodies that can be very specific to binding to anything we want to find. For example, sometimes the tumours, not only do they shed little molecules out into the blood, but the cells themselves shed into the blood - that’s called circulating tumour cells. Circulating tumour cells have a molecule on their surface that makes them unique and we can have an antibody that finds that molecule and the antibody is attached to a little magnetic nanoparticle.

Isabelle - How do you decide what might be a useful molecule to look for?

Sam  - Based on progress in the early cancer detection world, we continue to find different molecules that are useful to go after. For example, with circulating tumour cells, those tumour cells have a molecule on their surface called EpCAM, and EpCAM if it’s found on a surface of a cell in the blood it’s highly likely to be a tumour cell. But, because those things exist in rare amounts you still need a solution like the mag wire to, in fact, sample the entire body’s blood volume. Because when a tumour gets smaller and smaller, whatever is going to be shed into the blood is present at lower and lower concentrations.

Isabelle - Does this mean that we can make the mag wire sensitive enough to eventually be useful as a screening test for cancer?

Sam - The mag wire could eventually be a screening test, although it’s more likely to be useful for high risk populations as opposed to the larger population that we would call low risk. And the reason is the mag wire would have to be left in for about 20 minutes and it’s unlikely that we would put millions and millions of people through a screening process where they would not get just a simple blood draw, but would have to have a wire in them for 20 minutes.

However, for people that are at higher risk that have family histories of cancer, have other history or genetic issues related to cancer, in those cases it may in fact make sense to use the mag wire to in fact detect if they have an early cancer.

Isabelle - Do we know if there are any risks associated with using the mag wire?

Sam - We don’t know about any risks yet. We continue to study that. There’s probably no significant risk from the wire itself; there may be some risk in the nanoparticles. The nanoparticles that one can use, are made of things like iron; different elements are magnetic but, we in fact give to humans iron based nanoparticles. We break down the nanoparticles and use the iron in the nanoparticle, so it’s not that unusual to actually give someone a magnetic nanoparticle. 

Georgia - To anyone else like me who was worried Chris has just been telling me that iron in your blood is not in a magnetic form so the magnet wouldn’t such out all of your blood.

Chris - Someone did write to us once and said don’t those people who work at dumps and car yards where they move old cars around with a giant magnet, wouldn’t they have something of a health problem if that were the case? And the answer is reliably no! You don’t have all your blood rushing to the magnet at the junkyard.

 

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