Cancer diagnosis without biomarkers
The Raman effect was used to search for cancer cells
Scientists from Harvard University have developed a technique that allows in vivo to observe the dynamic distribution of DNA in a cell without using any staining markers. The method is based on forced Raman scattering microscopy (Raman effect) and allows for non-invasive diagnosis of skin cancer, as well as to quickly assess the aggressiveness of cancer cells. Article by Lu et al. Label-free DNA imaging in vivo with stimulated Raman scattering microscopy is published in the Proceedings of the National Academy of Sciences, its contents can be briefly reviewed in the report Label-free technique that images DNA in vivo.
Forced raman microscopy (WRC) is a method for visualizing the vibrational frequencies of chemical bonds. Different types of bonds have different resonant frequencies depending on the molecular environment. For example, the vibrational frequency of the C-H bond in a DNA molecule is slightly different from the vibrational frequency of the bond in proteins and fats. Unlike traditional raman spectroscopy, WRC microscopy allows obtaining data about a sample in real time. This allows you to "see" the distribution of substances inside the cell and observe cellular processes without using fluorescent markers.
As a test of the new method, the researchers used WRC microscopy to search for cancer cells in skin samples. Previously, scientists investigated in vitro the efficiency of the method on the culture of human cancer cells HeLa. With the help of WRC microscopy, it was possible to construct a three-dimensional picture of the distribution of DNA, fats and proteins in the cell in the mitosis prophase: DNA was located in the nucleus, fats were mainly in the cytoplasm, and proteins were distributed throughout the cell.
Subsequent observations allowed us to "consider" the transition to interphase, metaphase and anaphase. Then the method from the culture was transferred to mouse and human skin samples. Scientists were able to distinguish all the stages of cell division in them, and also observed the migration of chromosomes. This made it possible for the first time to quantify the rate of mitosis in vivo and to determine the "aggressiveness" of cancer cells.
The study of human skin tissue confirmed the applicability of the method for histological diagnosis. WRC microscopy revealed an increase in the number of cell divisions, which is a distinctive feature of malignant cells. According to the authors, the new method is not only able to speed up surgical procedures by imaging tumor tissues, but also potentially applicable for preventive diagnostics.
To study cellular processes, it is necessary to "look" inside the cell without disturbing the ongoing processes. Usually, DNA imaging requires labeling with fluorescent markers. Such an approach is called invasive, the effect can change the processes occurring in the cell.
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14.09.2015