The immune system has the power to cure cancer. However, in order to harness this potential and enable the development of effective cancer treatments, we need a better understanding of how the immune system interacts with tumours. Recent research suggests that tumours can modulate the immune system, especially in advanced stages of the disease.
As a result, immune cells that would normally be able to attack the tumour are suppressed and no longer work effectively. We recently observed this phenomenon in a clinical trial of a melanoma vaccine. Whereas patients with early stage disease appeared to respond well to the vaccine, those with advanced melanoma (where the cancer had spread to other parts of the body) showed hardly any response.
Because the immune system is so powerful, it needs to be carefully controlled so that it doesn't attack healthy organs and tissues. One way that this is achieved is through a population of immune cells known as regulatory T cells (Tregs). Although Tregs are essential for keeping the immune system in check, and therefore preventing allergies and autoimmune disease, they can also block immune responses to vaccines.
We believe that Tregs may be responsible for the reduced effectiveness of our vaccine in patients with advanced melanoma. The aim of the present study, therefore, is to determine if Tregs are involved and, if so, how we can inhibit them to make the vaccine more effective.