PERSONALIZED MEDICINE

by Academician Mikhail PALTSEV, RAS and RAMS, First Vice-President of the RAMS, Rector of Sechenov Moscow Medical Academy in 1987-2009

Scientists of many countries are actively discussing the concept of personalized or predicative medicine in recent years. According to predictions, it can greatly improve the treatment quality. Early detection of risks of emergence of this or that disease in an individual and optimal medical care of this patient can become a reality in the near future.

"TREAT THE PATIENT, NOT THE DISEASE"

This approach is not new for Russia. Splendid physicians of the past, including one of the founders of Russian therapy Matvei Mudrov (1776-1831), who had developed a scheme of examination of the patient and introduced the recording of a disease history, regarded each patient as a unique combination of hereditary factors and acquired characteristics, manifesting themselves under specific conditions of life. No doubt, new data accumulated by specialists later contributed to more profound understanding of these concepts*. But even after deciphering of the human genome at the beginning of the 21st century we still

* See: S. Popov, "Medicine of Tomorrow Born Today", Science in Russia, No. 3, 2005.–Ed.

Algorithm of diagnostics by use of biological microchips.

have no answers to many important questions. It is still unclear how rather few genes keep the entire information about the structural and functional characteristics of an individual and provide so great a diversity of people on our planet. It is also unclear to what degree the genome determines the individuality of each of us and how much the environmental factors modify genotype manifestations.

Of course, these problems are in the focus of basic science interests; however, the solutions are directly connected with the actual treatment of patients. Just one example. In the 1970s the physicians in our country and abroad found that after injection of succinyl-choline (anesthetic), a part of patients easily woke up without consequences of any kind, while some patients had respiration problems after awakening and remained immobilized for some time. Examinations of the latter have revealed that delayed metabolism of this drug was genetically determined in them. As later studies have shown, 1 of 3,500 humans carries two copies of genes attributing him to the risk group with such side effects. This case was one of the first that have demonstrated a direct relationship between genetic variations and individual patient's reaction to drugs. A vast scope of data on genetically determined metabolic features of chemicals in humans have been accumulated since then. These data help us understand why the same drug is effective in one patient, ineffective in another, and toxic in still others. Similar cause-and-effect relation-ships, still not quite clear, play a key role in emergence of a certain disease with typical symptoms in different patients. For example, it was found that high risks of Alzheimer's disease and breast cancer development are associated with hereditary genetic characteristics. The emergence of lung cancer in a part of tobacco smokers and its absence in another part is explained similarly.

However, the established approach, implying that after the disease is diagnosed, all efforts of the physician are aimed at the treatment of the "disease" as a complex of symptoms (while the patient is as if separated from the psychosocial context and his characteristics are neglected) still predominates in differential diagnostics of diseases. With an approach of this kind all efforts aimed at the "disease" control fail, as a disease is a dynamic process, in which the individual patient's characteristics are essential for a disease prognosis and treatment efficiency.

In the 1990s, the specialist in functional medicine Leo Holland (USA) suggested a new approach, named "Patient-oriented diagnostics and treatment". In this model the creation of multifactorial database for each patient implies that his biological and psychosocial characteristics are taken into account. The total picture is constituted from numerous details–results of an analysis of the work of various body systems (in some cases at the molecular level), history of hereditary diseases and even... description of relationships in the family. The doctor eventually integrates behavioral, meta-

Scheme of a microchip for diagnostics of abnormal methylation (modification of DNA molecule) of genes involved in carcinogenesis.

bolic, constitutional, and ecological factors with the basic methods of differential diagnostics. Let us recollect that the word "diagnosis" (Greek) means "to learn through", "to find out to the end, thoroughly". This very meaning returns to the concept of "diagnostics" in Holland's model. And Mudrov's philosophy-"treat the patient, not the disease"–is realized at a new level by means of the most advanced technologies.

The year 1998 can be considered the year when personalized medicine was born. This term first appeared in the title of the monograph by Keval Jane, an American scientist, published that same year. The new trend is inseparably linked with molecular medicine, largely underlying the development of innovation technologies, based on cellular and biomolecular methods and means of diagnostics, prevention, treatment, and rehabilitation.

Let us emphasize that three classical aspects remain important for personalized medicine: disease prevention, diagnostics, and treatment (if it exists). Let us discuss them in detail.

PERSONALIZED PREVENTION

It includes search for genetically conditioned liability to development of this or that disease–the so-called "weak sites" of the body. Let us distinguish several main trends of research, which can be important for deciding on the extent of the individual characteristics of a human being can be vital from the point of view of predicative medicine.

It is envisaged to determine genetic peculiarities of a human being as a biological species that distinguish him from other representatives of the fauna–to make up a genetic map of Homo sapiens. It is not yet clear what kind of genes make a human being a human being and a disease–a human disease, that is, a condition related to specific biosocial and other factors intrinsic to humans. An "ideal health" document of this kind should be created for representatives of different races (nations) and their comparative analysis should be carried out. In addition, individual genetic maps are essential, evaluating the hereditary liability of an individual to socially significant diseases (immunodeficiency, cancer, endocrine and mental diseases, myocardial infarction, brain stroke, etc.). One of the most important tasks is detection of carriers of mutations associated with highly frequent monogenic diseases (phenylketonuria*, mucoviscidosis**, etc.) and dominant diseases with a late "debut" (Alzheimer's disease, diabetes, hereditary forms of breast cancer, etc.). Individual sensitivity to destructive effects of xenobi-otics (ethanol, narcotics, ionizing radiation, chemical and biological factors including viruses) should also be detected. And the idea of obligatory evaluation of the genetic status of individual patients and of patient populations should be supported by practicing physicians of different levels.

Personalized prevention will make it possible to develop clear-cut recommendations for prevention of these diseases (regular checkups and early registration, use of appropriate nonmedicamentous agents and drugs). For example, detection of a risk of malignant tumor development implies more frequent prophylactic examinations (twice a year) with obligatory screening tests (mammography, X-ray examination of lungs, gastroduodenoscopy (examination of the gastric and duodenal cavities), evaluation of prostate-specific

* Phenylketonuria is a hereditary disease associated with amino acid (mainly phenylalanine) metabolism disorders, leading to severe involvement of the central nervous system.–Ed.

** Mucoviscidosis is a systemic hereditary disease caused by gene mutation and characterized by involvement of the endocrine glands, severe respiratory and gastrointestinal dysfunction.–Ed.

Analysis of clinical specimens using a low density microchip for an analysis of methylation.

antigen, examination of smears from the cervix uteri, clinical blood analysis, etc.). This will help diagnose a disease at early stages, when highly effective therapy is still possible. Other recommendations (to give up smoking, diets, vocational advice) will promote (if followed) reduction of cancer risk (lung cancer, rectal cancer). In future these tests are advisable for the entire able-bodied population.

PERSONALIZED DIAGNOSTICS

The diagnosis based on biomarkers occupies an important place in personalized medicine (as we have already mentioned, many specialists regard it as a trend of molecular medicine). Biomarkers are biological compounds indicating the presence of some specific disorders or a susceptibility to develop them. Today we know the markers at the levels of cells and subcellular structures, but with the development of analytical methods, the markers at the level of genome, tran-scriptome*, proteome**, and metabolome*** will become available. The complex of such indicators will make it possible to evaluate the individual health status and predict the disease risk and probable course.

At present the efforts of scientists are aimed at search for molecular biomarkers and development of respective test systems. We have a practical result: the Institute of Molecular Medicine of Sechenov Moscow Medical Academy**** (Sechenov First Moscow State Medical University since 2010) in collaboration with the Institute of Theoretical and Experimental Biophysics, the Russian Academy of Sciences, in Pushchino (Moscow Region) started large-scale manufacture of biochips, biochemical sets for their development, and chip detectors with original software.

Certainly, the creation of systems of this kind implies good knowledge of the type of biological material analyzed at biological laboratories, for example, of an oncological profile. In the overwhelming majority of cases the object of analysis are paraffin-impregnated blocks containing a formalin-fixed tumor tissue. One more material for early diagnostics and monitoring of the cancer process in the near future will be patients' plasma specimens. These materials are not fit for analysis on the basis of classical expression microchips (as European experience indicates, irrespective of the probe application density). Nonetheless, the same specimens become fit for an analysis of nucleic acids present in them after amplification procedure (increase in the number of DNA copies); low density microchips are used in these cases. Their pilot variants for detection of "failures" in MGMT, RASSF1, GSTP1, RARß, CDKN2A, SFRP1, and HIC1 genes, involved in cancer emergence, have been created at the Research Institute of Molecular Medicine mentioned above.

Molecular diagnostics is rather effective in hereditary forms of cancer, for example, in retinoblastoma. It is a tumor of the eye retina; the malignant neoplasm rapidly metastasizes into adjacent tissues. It develops during intrauterine development or the first 2-3 years of life. Effective treatment and survival is possible only if the tumor is detected at an early stage. The comprehensive

* Transcriptome is a totality of all transcripts (RNA molecules) synthesized by one cell or group of cells.–Ed.

** Proteome is a totality of body proteins.–Ed.

*** Metabolome is a complete set of low molecular metabolites (intermediate products of metabolism, hormones, and other signal molecules), which can be found in biological specimens.–Ed.

**** See: M. Paltsev, A. Ivanov, V. Kiselev, "From Molecules of Disease on to Health Molecules", Science in Russia, No. 1, 2006.–Ed.

Gene therapy EX VIVO in the treatment of tumors.

molecular genetic studies of abnormalities in the RB1 gene (normally suppressing the development of cancer cells) in patients with various forms of retinoblastoma were carried out at the Research Institute of Molecular Medicine. Mutations of this gene were found in 90 percent of examined patients. The diagnostics was carried out in more than 200 patients and their family members. Hereditary nature of the mutations was confirmed in more than 30 percent of cases. This fact indicates that effective detection of liability to this pathology is quite possible.

The diagnostics at pre-symptomatic stages will help detect not only rare forms of cancer, but some nervous and mental diseases as well, which are now detected only by clinical symptoms. All this will serve as a prerequisite for development of effective treatment methods.

PERSONALIZED TREATMENT

Numerous pharmacoepidemiological studies indicate poor efficiency of drugs in various diseases. According to the data of the World Health Organization, some drugs are absolutely ineffective in 40 percent of patients. But this is so in case of a standard approach to patients. Individualized diagnostics of a disease suggests personalized choice of drugs. After detection of genetic characteristics of a patient, the doctor will choose the most effective and safe drug and its dose. This approach can be used in cardiology, pul-monology, rheumatology, psychiatry, neurology, oncology, transplantology, and other branches of medicine. It will promote improvement of the therapy efficiency and reduce the incidence of untoward reactions. In addition, it will reduce expenses on expensive drugs, which can be ineffective for a patient in case of an empirical choice.

The important trend of personalized medicine is detection of polymorphisms (differences) of the key genes, determining the treatment strategy in many diseases. For example, the efficiency of treatment of some cancers depends on the presence of mutations in KRAS, p53, HER2, and some other genes.

Individual approach has been actively used in cell therapy of cancer in recent years. The importance of this trend is explained by high resistance of tumor cells to various drugs. Therefore, creation of vaccines with "personal address" is expected to improve the treatment efficiency in these diseases. Search for personalized protocols of cancer control therapy is in progress at the Research Institute of Molecular Medicine. What are the specific features of this treatment?

Patient's tumor cells are cultivated in the presence of the vector containing the gene coding for production of a cytokine (peptide regulatory molecule) or a toxic product. At the next stage after transfec-

Vaccination using antigen-presenting cells.

tion* they are cultivated to increase their count and then exposed to radioactive radiation, as a result of which they can no longer divide and propagate in the body. Then they are injected to the patient. This stimulates the immune system recognizing the protein produced by transfected cells, this eventually leading to destruction of tumor cells.

Among the innovation methods are methods for creation of individual cell vaccines and immune response regulation using dendritic cells** and adaptive immunotherapy methods. Numerous clinical studies (by today more than 1,000 drugs based on these cells have been tried) have demonstrated safety, good tolerance, absence of side effects, and efficiency of these cells in melanoma, renal cell carcinoma, prostatic cancer, gastrointestinal tumors, and cancers of other localization, including pediatric oncology. The trials have shown that immunotherapy by autologous dendritic cells (originating from the organism of the patient) brings about a good clinical result in at least 30 percent of cases. Studies aimed at improvement of the efficiency of these vaccines are in progress at the Research Institute of Molecular Medicine. The goal is development of methods for cell therapy of all cancer types. The most promising in this sphere are antigen-presenting cells***, in vitro conditions transfected by the vector for tumor cell destruction and then injected to the patient.

One of the aspects of personalized medicine are therapeutic methods based on autologous stem cells. These technologies are already widely used for the treatment of cardiovascular diseases, cancer, and in regenerative medicine.

* Transfection is an injection of a foreign nucleic acid into human and animal cells.–Ed.

** Dendritic cells are one of the immune system cell types.–Ed.

*** Antigen-presenting cells are a heterogeneous population of leukocytes with a pronounced immunostimulatory activity; they are located in the skin, lymph nodes, spleen, mucous membranes, and thymus.–Ed.