Not all in the genes...
This week was the 10-year anniversary of the initial decoding of the 3 billion base pairs of the human genome. The research effort was through the $3 billion public-funded Human Genome Project and its privately-funded competitor, Celera Genomics. Even before the genome was fully mapped, forecasters spoke of the new age of “personalised medicine” where we would be able to have genetic tests to tell us about our own specific disease profile. President Bill Clinton made patenting of individual genes illegal. This hype and excitement led to unprecedented investment in genome-wide scanning across almost every disease category in the human body over the past decade.
However, even in the early stages of the project, some commentators showed concern regarding the level of spending and the concentration of research on gene mapping, as well as the massive ethical implications of knowing the genetic make-up of an individual and how to use the data. Unfortunately it was the predictions of these commentators which proved to be right a decade later.
There is no doubt that genome-mapping has added to our scientific understanding of new disease pathways and the causation of disease, but the practical application and translation of any new knowledge into new drugs or treatments has been lacking, as this week’s Lancet notes. Outside of a few cancers and some very rare inherited disorders, common diseases such as coronary heart disease, bowel cancer or stroke have turned out to be impossible to map by genes alone.
Individual risks associated with individual gene variations are generally very small and these variations are common, which means that we are unlikely to be able to predict risk of disease on the basis of this information alone in individual patients. The exceptions are diseases due to single genes (e.g. cystic fibrosis) or diseases where the genetic risks explain a large proportion of the disease, such as age-related macular degeneration. The focus of research is therefore shifting to gene-environment interactions and trying to explain the variation in susceptibility to disease between individuals.
The concept that diseases are the outcome of both genetic and environmental interactions is far from new. In the 9th century AD, Al-Jahiz considered the effects of the environment on the likelihood of an animal to survive, and first described the “struggle for existence”. Therefore, even in the age of genome-wide scanning, old techniques such as family history studies remain the most accessible way of measuring the inherited component of a disease and represent the overall interaction between environmental and genetic factors. Family history studies are still required to guide or focus genome-wide scans, in order to decide which analyses may be useful (e.g. by sex, age, risk factors).
All scientific discovery has historically taken time to translate into clinical practice and so we must wait to see what the future holds for genomic mapping and it application in patient care. However, in the age of tighter budgets and increased accountability, should research spending be governed more by evidence of the scientific fruit that it bears? Or is it enough for medical research to push back the boundaries of knowledge, regardless of the usefulness to patients?