3D hydrogel biochips helped in cancer detection
Researchers from the Moscow Institute of Physics and Technology, the Institute of Molecular Biology, the Institute of Bioorganic Chemistry and a number of other Russian research centers have developed a new approach to the diagnosis of intestinal cancer. The development is described on the pages of the journal Cancer Medicine (Butvilovskaya et al., Multiplex determination of serological signatures in the sera of colorectal cancer patients using hydrogel biochips).
Scientists have developed a special biochip based on a hydrogel that allows you to diagnose intestinal cancer, also known as colorectal cancer or CRC. This oncological disease ranks third in frequency among all malignant neoplasms, and in the first stages the disease proceeds with minimal symptoms. The five–year survival rate of patients with CRC, despite all the efforts of doctors, still does not exceed 36% - it is possible to achieve a good therapeutic effect and recovery of the patient only with timely diagnosis of colorectal cancer.
Currently used diagnostic methods are imperfect. In vitro assays conducted "in vitro" have low specificity, and invasive methods like colonoscopy are not only traumatic, but also do not always provide for early diagnosis, since they do not allow to cover the full picture of the development and spread of CRC.
The method proposed by scientists from the IMB RAS, MIPT, RSCC, I.M.Sechenov First Moscow State Medical University, IBH RAS and the V.M. Buyanov City Clinical Hospital is based on the simultaneous detection of many different substances in the blood of patients at once. These are autoantibodies against oncoassociated glycans (found in blood serum in the early stages of cancer), immunoglobulins of various classes, as well as cancer markers, molecules produced by tumor cells.
What ?
Cancer markers are substances that are already actively used to diagnose cancer. However, the combination currently used for the diagnosis of CRC (carcinoembryonic antigen + carbohydrate antigen CA 19-9) provides not too high sensitivity: allowing only half of the cases of the disease to be detected. To increase the sensitivity of diagnostics, researchers turned to glycobiology, an actively developing scientific discipline about glycans, the most important biological molecules.
The most famous glycans are starch, chitin and cellulose; from the point of view of chemists, glycans are called biopolymers formed by chains of monosaccharides (glucose and fructose are examples that are known to non–chemists), "cross–linked" by glycoside bonds (a bridge from an oxygen atom). In the life of the body, glycans play the role not only of nutrients or "building materials" for cells, they are important for establishing contacts between cells, for the proper growth of organs and much more. In the context of the new study, it is especially important that cancer cells have special glycans: molecules that make it possible to distinguish these cells from healthy ones.
Autoantibodies allow to identify oncoassociated glycans. Antibodies are molecules that the immune system produces for a highly precise fight against a specific enemy and they are finely "tuned" to interact with a given target. For example, antibodies against the influenza virus interact only with a protein that is part of the viral particles of a particular strain, and autoantibodies against oncoassociated glycans interact strictly with glycans that are present only in cancer cells of the CRC.
Antibodies make it possible to mark a target and activate mechanisms that ensure its destruction. Moreover, the target may also be the cells of the body itself: if they have been reborn into cancerous ones or have been infected with viruses. The unique ability of antibodies to selectively detect other molecules has formed the basis of many methods of laboratory diagnostics, and is also actively used in scientific experiments.
How?
The researchers suggested looking for autoantibodies to oncoassociated glycans in the blood serum. This method has already shown its promise in the diagnosis of ovarian cancer (in 2012, a corresponding publication by Swiss scientists was published), and biological microchips were chosen as the main diagnostic tool.
The idea of microchips in the 1980s was proposed by Andrey Mirzabekov, who headed the Institute of Molecular Biology and the Department of Molecular Biophysics at MIPT; today this idea is called the technical basis of biology of the XXI century. A microchip is, in most cases, a flat plate with samples of certain biological molecules applied to it – and in the new article we talked about such a development as a three–dimensional biochip based on a hydrogel.
Such chips are being developed at the IMB RAS and they are volumetric cells made of a special gel, inside which the necessary reagents are located – molecular probes. The structure of the gel provides an optimal environment for analysis, and the researchers have successfully solved many problems that stand in the way of accurate diagnosis: for example, they managed to achieve a uniform distribution of molecular probes and provide sensitivity superior to conventional "flat" (or, as experts say, planar) systems.
What did you get?
Researchers have created a prototype test system that allows to simultaneously measure the concentration of protein-based cancer markers, autoantibodies to glycans, as well as immunoglobulins G, A and M in human blood. Taking into account the fact that most protein markers are not specific in relation to the localization and type of tumor, scientists have combined them into groups – the so-called diagnostic and prognostic signatures (combinations of protein cancer markers and antibodies to glycans, etc.).
Drawing from an article in Cancer Medicine – VM
Using the created prototype, the scientists analyzed the blood sera of 33 patients with CRC, 69 healthy donors, as well as 27 patients with inflammatory bowel diseases. Diseases like Crohn's disease or diverticulitis can lead to CRC in the long term, but it is highly undesirable to confuse them with each other when diagnosing the disease – the laboratory analysis system must be not only sensitive, but also accurate.
This approach has allowed us to surpass modern methods. With the help of a prototype test system based on diagnostic signatures, it was possible to correctly predict the diagnosis of CRC in 95% of cases, against 79% determined by the traditional method. The sensitivity of detecting CRC (patients with stage II-IV CRC) was 87% versus 21%: such an increase is certainly a significant achievement. The specificity of the method was 97%.
The sensitivity of a diagnostic technique is its ability to detect a disease during testing. The higher it is, the better, but sensitivity alone is not enough to make a diagnosis: the diagnosis should also be correct and in cases where it is a question of some other diagnosis, the method should not indicate cancer in its absence.
It is the ability to accurately predict the diagnosis that is expressed by the first number of 95% – on average, in 95 patients out of 100, the disease will be determined correctly. The sensitivity of 87% indicates that out of 100% of cases in patients with CRC, 87% will determine CRC. The traditional method of detecting CRC showed a sensitivity of 21%, which means that some patients with CRC will be recognized as healthy. And if there are patients with inflammatory bowel diseases among all patients, cancer will be correctly identified in 97% of cases.
"The method developed at the IMB RAS is extremely promising for helping in the diagnosis of gastrointestinal diseases, and we hope that test systems based on this method will soon appear in clinical laboratories of our country," Zhanna Zubtsova, Ph.D., Associate Professor at MIPT, one of the authors of the developed approach, shared.
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01.06.2016