Why does cancer kill you?
Gerard said earlier that all cells want to expand and grow and live. So why does cancer kill you? Why don't you just end up as some massive big cancerous blob that lives forever rather than die?
That's actually an important question and one of the questions I ask my students when I'm teaching: why does cancer kill? It's not simple. I think what it tells us is that if cells don't grow in the right way and they start mucking up the blood supply and the nerves and the normal function of tissues, your body can't cope and that's what kills you. So cancers basically erode the normal functions of your organs and your tissues, and that's why it kills you, although different cancers kill in different ways. In fact you can keep cancer cells growing forever, you can take them out of a patient and put them in a petri dish and off they go forever and ever. There are some cancer cells that have been around for so long that they mass of cancer cells in the world is something like a thousand times that of the original patient. So in principle you could live forever as a large lump, but I wouldn't want it.