Training your white blood cells to kill off cancer cells?

Don't want to get your hopes up, it is not here yet but researches are exploring this method where they are able to 'train' your white blood cells to recognize cancer cells and whack the *^&# out of the cancer cells.

If this method works, it is like using our own body mechanism to fight off cancer. I hope the day where fighting cancer can just be as simple as an injection (something like a flu shot) and our white blood cells once given the 'blueprint' of the cancer cells will go after them and kill them.