Analysis Of Sialic Acid Abnormal Junction In Serum Of Patients With Liver Cancer Based On Specific Derivatization

Liver cancer is one of the most common malignant tumors in the world.Hepatitis B virus infection is one of the main causes of liver cancer.Hepatitis B virus can stimulate liver cells for a long time,cause cirrhosis and promote the occurrence of liver cancer.Early stage liver cancer does not have obvious clinical symptoms,many patients are in the middle and late stage when found.Therefore,the early diagnosis of liver cancer is of great significance to reduce the mortality of liver cancer.Studies have found that the development of liver cancer is accompanied by abnormal sialic acid modification.Sialic acid is a kind of acidic nine carbon monosaccharide,which mainly exists in the form of N-acetylneuraminic acid in human body and is mainly located in the reducing end of protein sugar chain modification.As an important post-translational modification of proteins,sialic acid modification is usually carried out in the form of C2 hydroxyl group α 2,3 or α The 2,6 glycosidic bond is linked to galactose.Abnormal sialic acid modifications of proteins include the overall level of sialic acid modification and the way of sialic acid connection.Studies have shown that the analysis of serum protein sialic acid connection in patients with liver cancer is helpful to the development of early diagnosis of liver cancer.However,limited by technical means,abnormal sialic acid connection can not be detected directly and accurately.In this study,the molecular weight of sialic acid residues was changed by isopropylamidation and methamidation of sialic acid residues with different ligation modes.Matrix assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS)was used to detect sialic acids with different molecular weights.Firstly,serum N-glycan was immobilized by hydrazide beads,and sialic acid derivatization was carried out twice in succession α 2,3 sialic acid linked methyl,α 2,6sialic acid is linked to isopropyl,resulting in poor quality.N-sugar was eluted from hydrazide beads to complete the whole methylation step and desalination step.Using MALDI-TOF-MS analysis,the quality of sialic acid with different molecular weight can be detected.Next,this study used four different sources of serum samples,which were hepatitis B related liver cancer patients,non hepatitis B related liver cancer patients,liver cirrhosis patients and healthy controls.The original data of MALDI-TOF-MS were obtained by specific derivatization method.The original mass spectrum data were preprocessed by clinpotools 3.0 software.The data uniformity and data difference between groups were analyzed by drawing spectral view and gel view.The results showed that there was a significant difference in the relative intensity of H5N3E1 peak between HCC group and non HCC group(p < 0.001);There was significant difference in relative intensity of H4N4F2E1 peak between HBV related HCC group and non HBV related HCC group(p < 0.001);The relative intensity of H6N5F1E1 peak was significantly different between cirrhosis group and healthy group(p < 0.0001).This study developed a method to analyze the abnormal sialic acid connection and find the sialic acid peak with significant difference among different groups.By using this method,the detection of liver related diseases was completed.A group of sialic acid modified n-glycochains were found to have significant differences in the expression level among different groups,so as to find new tumor markers for liver cancer The positive hints of the tumor markers and liver cirrhosis markers of liver cancer related to hepatitis B provide a new direction for early diagnosis of liver cancer.