Dendritic Cells, cancer vaccine and Immunotherapy explained
What Vaccines are Available?
Dendritic cells, cancer vaccines and immunotherapy explained.
There is a great deal of scientific and clinical evidence that indicates that the immune system is involved in the destruction of tumours. Immunotherapy for cancer involves the use of agents that modify immune responses and has been used since as early as the late 19th century. Many approaches that constitute immunotherapy are in common usage today; interleukin-2 is licensed for use in renal cancer and BCG, a killed bacterial preparation, is used in the treatment of bladder cancer.
Cancer vaccines are a way of boosting an immune response specific to a tumour to eradicate it from the body. Everyone is familiar with the vaccines that are given in childhood to prevent the establishment of a disease, but cancer vaccines differ in that they are given after the disease has become established. There is no question that this approach works and indeed, for some types of vaccine, 10-20% of patients achieve some clinical benefit. However, there is still much research to be done in order to improve these vaccines.
One of the best approaches so far is the “dendritic cell” vaccine. The function of dendritic cells is normally to look for foreign material (for example from a bacteria or a virus) and then to use this material to instruct the immune system to fight off a particular disease. Scientists have hijacked the dendritic cell’s ability to pick up foreign material (antigens) in order to make vaccines: Dendritic cells can be taken out of the blood, exposed to tumour extracts in culture and then reintroduced into the body as a vaccine. The resulting dendritic cells can educate the immune system to respond to the tumour antigens and kill the cancer.
There is a huge store of knowledge about dendritic cells but this understanding must be converted into a clinical application. To this end much of the research done at St George’s University of London aims to improve vaccines through understanding the best ways to manipulate dendritic cells. Our research programmes extend into compatible areas of immunology that may allow us to exploit other cells of the immune system (for example gamma-delta cells) and to prevent natural processes that normally suppress immune responses against a tumour.
Although historically only about 10 to 20% of patients respond to vaccine therapies, recent advances led to an understanding of some of the underlying reasons why vaccines do not perform better. Research to overcome these problems falls into three general areas;
1. Research into basic tumour immunology has shown that many aspects of a tumour’s natural progression protect it against attack through evasion or suppression of immune responses. Thus much effort is now being put into ways of improving vaccine therapies using approaches that overcome these innate problems. Many of the approaches taken to solving this problem involve immunotherapy, often using drugs that resemble, or interfere with, molecules involved in the normal function of the immune system.
2. Which 10-20 % of people are going to respond to their treatment? Many groups have embarked on research programs with a view to the development of tests for identifying responders to vaccine treatment, which in turn should improve the overall success rate of immunotherapy.
3. Finally, although the proponents of chemotherapy and immunotherapy have long kept their studies separate it is becoming clear that these two approaches may, in some circumstances, be mutually compatible. In the future we stand to develop new treatments based not only on the standard “vaccine” approach but ultimately, with improved understanding of tumour biology, we may be able to manipulate the immune system to kill tumours with appropriate drug treatments.
Cancer vaccines have proven themselves to be effective and safe to such an extent that major interest has been shown by some of the big pharmaceutical companies and several important phase III clinical trials are currently planned or underway to test vaccines in lung, prostate, renal and colorectal cancer. However, more research is required to develop these very useful technologies to the point of every-day clinical application.
What Cancer Vaccines are Available at St George’s University of London?
Cancer vaccines are a relatively new type of treatment and, as they are still in early stages of development, are currently only available to patients through clinical trials. These trials are important to rigorously test the safety of vaccines and to make sure that the treatments really do work. Trials typically take many years and unfortunately, reports in the newspapers and on television about 'miracle cures' can be misleading. The CVI is not funding any trials at present, but several future trials are planned (see future clinical trials).
