Does cancer get past our immune systems?

Immunologist Clare Bryant took on this one. First of all, Chris asked, does cancer evade the immune system?

Clare- Well, most of the time, no, actually, because your cells are growing and proliferating all the time. What happens when a cell proliferates is it can have a mutation, tends to be a small number of cells in the immune system will whip them out. So what actually happens, um, when you get cancer, that is a problem, is that your cells, that are proliferating and that are mutated, they really outgrow the rate at which the immune system can take them out. The other thing that cancer cells do is they can express, under normal circumstances cells will express, "eat me" signals, and then T-cells or macrophages will come along and chew them up. Sometimes cancer cells can actually switch off the "eat me" signal and at that point the cell becomes invisible to the immune system and the immune cells just pass it by.

Chris -   And is therefore, when you get a cancer, is that effectively a failure of the immune response then? It's escaped and it's managed to form a tumour?

Clare- That is exactly one of the mechanisms by which it happens. And of course there are now a whole host of immune therapies which are working super efficiently to actually really get rid completely of these cancers. So it's a very exciting area and that the data coming through on these immune therapies is really, really interesting and exciting.

Chris-   The rationale being if the immune system can get rid of cancer in the first place, all we have to do is reprogramme it to do that - I say all we've got to do, but basically - redeploy the immune system and overcome whatever's held it back. To get rid of the cancer.

Clare- That's exactly the theory and it does seem to be working really well.