The value of genomics and personalized medicine is mistakenly underestimated
Earlier this month, the on-line version of the New York Times published the headline "The results of the study demonstrate the limited capabilities of DNA analysis in relation to disease prediction" ("Study Says DNA's Power to Predict Illness Is Limited". Does this mean that the genome does not determine a person's state of health? Who could have thought of such a thing?
First of all, many experts in the field of human genetics. Even specialists who have fully devoted their work to the study of genes associated with an increased risk of developing certain diseases readily admit that only a small number of such genes can help in predicting a person's fate. In most cases, hereditary risk is not an absolute prognostic factor.
Neil Risch, a leading specialist in statistical genetics and director of the Institute of Human Genetics, part of the University of California, San Francisco, agrees with one of the main conclusions given by the authors of the article, and the opinion of a number of experts quoted in it.
He also believes that the results of the genome study are of great value in terms of their potential to improve understanding of the mechanisms of development of various diseases on a global scale, and not in terms of their prognostic significance for a particular patient.
The days of "skimming the cream", that is, the identification of genes, the inheritance of which, occurring according to Mendel's laws, inevitably leads to the development of a particular disease, for example, Huntington's disease or cystic fibrosis, have already passed. Today, researchers are using new technologies to search the human genome for countless genetic variations that have less pronounced effects on the risk of developing diseases.
However, as the rate of information receipt increases, the number of identified DNA variants associated with human diseases will inevitably increase.
Therefore, the article by Nicholas J. Roberts et al. The Predictive Capacity of Personal Genome Sequencing, published on April 2 in the journal Science Translational Medicine, the authors of which modeled the importance of genomics for disease prediction and refuted scientific dogma, stating that in the future knowledge of individual genomes will have virtually no meaning for us, causes undisguised surprise. Population geneticists quoted in the competing news blog Nature Press consider this study to be unproven, and the model used in it to be incorrect. They also note that the active dissemination of information in the press that casts doubt on the value of genome research can harm the public.
Thus, carriers of genes that cause a very high probability of developing a particular disease, for example, heart disease, may decide that the risk is overestimated, ignore recommendations for lifestyle changes and completely rely on fate.
The time for personalized medicine has already comePersonalized medicine, which is based on making decisions about the prevention and treatment of diseases based on the results of laboratory analysis of the levels of certain molecular markers, is gradually becoming a reality.
Oncological patients were the first to feel the benefits of this approach, the results of genetic tests of which already allow determining the nature of drug metabolism and the probability of tumor response to treatment.
There are genetic tests that reveal an exceptionally high risk of developing certain types of breast and ovarian cancer. Women with a family history of the disease and with positive test results may take measures aimed at reducing the risk, while others who do not have a "risky" variant of the gene may experience significant moral relief.
Also, despite the lack of effective treatments for Alzheimer's disease, many people would like to know if they are carriers of ApoE gene variants associated with a high risk of developing this disease.
Risch does not claim that genes contain the answers to all questions, and does not discuss statements according to which environmental factors have a strong and underestimated influence on the development of even those diseases in the etiology of which there is a pronounced genetic component. In addition, a recent study conducted under his leadership showed that one of the main causes of the development of autism is an unidentified external factor to date. He also notes that in cases of many diseases, including type 2 diabetes, a person's lifestyle and behavior can have a significant impact on his health, regardless of genetic background.
However, the work under discussion and its coverage in the media can reduce the value of genomics in the eyes of society.
In fact, the more human genomes researchers sequence and the more they identify genetic variants associated with various diseases, the higher the prognostic significance of information about the personal DNA sequence becomes.
Inadequate research schemeThe study, the results of which are discussed in the New York Times, was published by a well-known biologist from Johns Hopkins University, Bert Vogelstein, with co-authors.
It is a model study based on the results of an analysis of the incidence of diseases in identical twins, and not the results of an analysis of real data conducted to identify specific risk factors.
According to the comments of geneticists in the Nature blog, the authors applied an unrealistic model and did not use standard statistical methods used by geneticists to model the risks of diseases caused by genetic variations within populations for data processing.
Genetic and epidemiological studies are conducted according to a variety of different schemes. When carrying out such work, both identical (having completely identical genotypes) and fraternal (whose DNA is identical by 50%) twins are usually considered. Risch considers incorrect statements such as "since identical twins have identical genotypes, and the probability of developing the same disease is less than 100% or only moderate, then genetic variations are a weak prognostic factor." He believes that the availability of data obtained only for identical twins does not allow us to determine which model is more suitable for analyzing these data. To determine a truly adequate model, it is necessary to conduct real genetic studies.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of California, San Francisco:
Value of Genomics and Personalized Medicine Is Wrongly Downplayed.
19.04.2012