| Gastric cancer is one of the most common malignant tumors. The prevalence and mortality in the world are high, as well as in China. Pathogenesis of gastric cancer often includes normal gastric mucosa - atrophy - intestinal metaplasia - dysplasia– cancer. Cancer cells could be divided into high, medium, low, undifferentiated cells according to malignant extent. The generation of different abnormal cells is due to the changes of the internal structure of cells. Studying the characteristics of different stages of cell structure, is helpful for understanding the procedure of gastric cancer better.Raman spectroscopy is a sound method in studying spatial structure of material. Raman spectrum is generated due to the high frequency non-elastic scattering of the molecular to incident light. There are many advantages using Raman spectroscopy to test biological samples, such as, no strict in sample forms whatever gas, liquid or solid, no strict in quantity, not susceptible to interference from water, no damage to sample, high test speed, good capability of real-time diagnosis and dynamic observation, and avoiding fluorescence interference using near-infrared laser. Raman spectroscopy is quite suitable for biological sample testing, which has been widely used in biomedical fields.At present, Raman spectroscopy has been applied to study tissues, cells and others, and to observe dynamic changes in cells according to measured Raman spectrum, etc. But there is no report on using Raman spectroscopy to study different gastric mucosa cells in the procedure from normal to cancer. We have differentiated and analyzed the Raman spectra including normal gastric mucosa, intestinal metaplasia, cancerous cells and genomic DNA, and different differentiated gastric cancer cells line genomic DNA, shown as follows:1. Raman spectra of the cell nucleus of HE stained gastric normal tissue, intestinal metaplasia and adenocarcinoma, were measured and comparatively analyzed using confocal Raman spectroscopy. Results suggest that the Raman spectra are similar between normal and intestinal metaplasia tissues, while the Raman spectrum of the adenocarcinoma tissue is significantly different from the other two. It is very easy to distinguish whether the tissue is cancerous tissue. Compared with the other two, the characteristic peaks of the Raman spectrum of the cancerous tissue are mainly: 1) peaks at 600 900 cm-1, 963cm-1 exhibit relative stronger intensity, which suggests that the content of the nucleic acids, proteins, carotenoids in cancerous tissue are higher; 2) peak at 1088 cm-1 might be due to the frequency change of the phosphorylation backbone original at 1090 cm-1, simultaneously with intensity decrease, which indicates that DNA chain has broken; 3) on the contrary, compared with normal tissue, peak intensity at 1610 cm-1 is much weaker than that at 1526 cm-1, which tells that the content of protein in cancer tissue decreased compared with lipid carotenoids.2. The Raman spectra of the genomic DNA extraction liquid of the normal gastric tissue, intestinal tissue and cancerous tissue, are measured by combining cell genomic DNA extraction technology and Raman spectroscopy. After comparatively analyzing the measured spectra, it is suggested that the gastric normal tissue genomic DNA has stable phosphate backbone; the Raman peak intensity of intestinal metaplasia genomic DNA at 1090 cm-1 is lower than that at 1050 cm-1, which indicates that its phosphorylation back bone becomes unstable; for the Raman spectrum of adenocarcinoma genomic DNA, two peaks appear at 1090 cm-1 band, which is much stronger than that at 1050 cm-1. It suggests that DNA chain broken and re-formed a stabilization structure. Peaks at 950 cm-1, 1010cm-1, 1100 1600cm-1 were different from normal tissue DNA, indicating deoxyribose and DNA bases may cause structural symmetry change due to chain broken. All these results indicate that the DNA variation process during the occurring process of adenocarcinoma may be: the stable DNA phosphate backbone in normal gastric mucosa changes into unstable DNA phosphate backbone in intestinal metaplasia issue under affecting of pathogenic factors, and finally DNA phosphate backbone is broken and re-forms a double stabilized phosphate backbones, which causes the occurring of adenocarcinoma.3. Raman spectra of the extracted DNA solutions from cultivated normal (GES-1), well-differentiated (MKN-28), differentiated (SGC-7901), poorly differentiated (BGC-823) and undifferentiated (HGC-27) gastric mucosa cells, are measured by using surface enhanced Raman spectroscopy technology. After carefully analyzing the spectra, we find that Raman spectra of normal gastric mucosa cells and high differentiated cells genomic DNA, are very similar, except that intensity of the peak at 1010 cm-1 is slightly stronger, for MKN-28; for the Raman spectra of medium, low and undifferentiated cells genomic DNA, the lower differentiated extent, the stronger intensity of peaks at 750-800cm-1, 890cm-1, 960cm-1, 1010cm-1 are, and weak peaks at 1060cm-1, 1090cm-1 also appears. Experimental results shows that more Raman vibration modes are excited in the higher degree of malignancy cells, as well as exhibiting stronger intensity, which indicates the conformation of the DNA is more diverse in the poorer differentiated cell, even broken. It also tells that whole DNA charge of the cancer cells may be changed, compared with normal cells.Systematicly studying the Raman spectra of gastric carcinogenesis is helpful to understand structure change better during canceration procedure, which is also helpful to apply Raman spectroscopy to clinical disease diagnosis, early diagnosis, research pathogenesis, observed efficacy, etc. In this paper, we applied the Raman spectroscopy for detection the normal gastric mucosa, intestinal metaplasia and cancerous cells and genomic DNA, and different degrees of gastric cancer cell line genomic DNA. It provides a new method for discovering the mechanism of gastric cancer, clinical early diagnosis, etc. |
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