Prof David Bowtell—Cracking the cancer code
Cancer is a worldwide problem. While cancer particularly affects the developed world, developing countries are catching up. It is essentially an age-related disease. In Australia, some cancers have become less common over time (e.g. colon and rectum, due to use of refrigeration for preservation of food), while others have increased (e.g. lung cancer due to uptake of smoking in women). Cancers vary greatly in their 5-year survival rate, but the general trend has been for survival to improve over time. Cancer is not a single disease, as shown by the variety of causal factors and different survival rates.
Researchers now have a substantial knowledge of the biology of cancer. Genetics plays a major role. Some people inherit mutations that predispose to cancers. People may also develop cancer because of the ‘adding up’ of the effects of genetic variants that give a small increase in risk. For others, environmental exposures are important. David drew an analogy between the way cells in the body operate and a computer—both have operating systems. In cells, the DNA encodes the operating system. Some people have ‘poor operating systems’ to start with (e.g. genetic mutations).
The price of genetic sequencing is rapidly coming down. There is now an international consortium trying to get a complete blueprint of all mutations causing cancer.
Traditionally, cancers were classified by taking samples of cancer tumours and looking at the anatomy. Nowadays, this is done by looking at the genetics. Classification of cancers comes out very differently when based on the genetics. For example, ovarian cancer is not a single disease, but a range of distinct diseases, some of which do not arise in the ovaries.
There is now molecular targeted therapy, which is specific to the genes that are driving the cancer growth. Drugs have been developed to inhibit the specific protein produced by a cancer-causing gene. The initial results are impressive, but eventually there is resistance as the cancer evolves. This is similar to antibiotic resistance. The future may involve combination therapies which reduce the risk of resistance.
Immunogenetics is the next frontier. This is based on how the immune system interacts with cancer cells. The aim is to overcome the blockage which prevents the immune system from killing the cancer cells.