One problem with trying to use the immune system to destroy cancer cells is that the body does not recognise these deadly cells as dangerous because they have evolved from normal healthy cells.
This is why, unlike an infection, the immune system does not destroy these cancer cells.
By using a virus to carry the gene therapy into the tumour cells, the cells self-destruct, which then alerts the immune system to launch a massive attack.
A new gene therapy technique is able to modify prostate cancer cells so that a patient's body attacks and kills them, US scientists have discovered. The technique causes the tumour cells in the body to self-destruct, giving it the name 'suicide gene therapy'.
Their research found a 20% improvement in survival in patients with prostate cancer five years after treatment. This new research genetically modifies cancer cells so that they signal a patient's own immune system to attack the cells.
Read more here