Study On Metabolic Biomarkers For The Diagnosis Of Early Colorectal Cancer

Colorectal cancer is the second mortality rate of cancer worldwide.The pathogenesis associated with the development of colorectal cancer has not been explored,and the disease can also metastasize to tissues and organs in other parts of the body.Treatment of colorectal cancer at an early stage has greatly improved patient survival.Since most colorectal cancer patients are diagnosed at advanced stages of cancer,this makes the treatment of colorectal cancer difficult.Therefore,there is a need to develop a highly accurate and less invasive method for the early diagnosis of colorectal cancer.Blood metabolite biomarkers are considered to be good options.Although many studies on blood metabolite markers of colorectal cancer have been reported,few biomarkers have been used for biofunctional validation as well as clinical practice.In this thesis,we firstly analyzed metabolic molecules in colorectal cancer plasma samples by liquid-phase mass spectrometry(LC-MS),combined with transcriptomic data from colorectal cancer tissue samples to screen biologically significant biomarkers,and explored the process of colorectal cancer development through functional validation of metabolic molecules.Secondly,the metabolic molecules of different types of immune cell samples from colorectal cancer patients’ blood were analyzed by metabolomics to investigate the effects of metabolic dysregulation on the immune system.Finally,the evolution process from colitis to colorectal cancer was simulated by establishing the AOM/DSS mouse model to achieve dynamic monitoring of the development process of colorectal cancer,in order to achieve early diagnosis of colorectal cancer with precision and provide a new idea for early diagnosis of colorectal cancer.The main research of this thesis is as follows.1.Exploring the determinants of colorectal cancer development based on metabolomics and transcriptomicsThe metabolic profiles of 128 plasma samples(88 plasma from colorectal cancer patients and 40 plasma from healthy volunteers)were used to investigate the changes of metabolic levels in colorectal cancer plasma samples.We also correlated the transcriptomic data of 84 colorectal cancer tissues,and used the combined multi-omics analysis of the two data sets to elucidate the metabolic dysfunction pathways of colorectal cancer cells and to identify the differential metabolite molecules associated with colorectal cancer.By considering early colorectal cancer as "part" and colorectal cancer as "whole" and combining "part" and "whole",a pathway of abnormal changes in plasma samples centered on lipid metabolism in colorectal cancer has been successfully identified.Importantly,it was observed that plasma levels of oleic acid and10 E,12Z-octadecadienoic acid(FA(18:2))metabolism were much higher in colorectal cancer patients than in healthy subjects.Finally,biofunctional validation of metabolic molecules confirmed that oleic acid and FA(18:2)promoted the proliferation of colorectal cancer tumor cells and could be used as plasma biomarkers for early colorectal cancer.2.Metabolic alterations of colorectal cancer immune cells based on metabolomics analysisBlood was collected from healthy volunteers and colorectal cancer patients,and four types of immune cell samples,T,B,NK and macrophages,were sorted out.The samples were analyzed using a high-resolution UHPLC-Orbitrap platform to optimize the mass spectrometry analysis method,and a PCA analysis model was established,which revealed significant differences in immune cell metabolism between the healthy and cancer groups.According to the metabolomics data,the metabolic pathways where the differential compounds of the four immune cells were found,among which,the glycerophospholipid metabolic pathway was significantly dysregulated and all other metabolic pathways were lipid metabolic pathways.Further screening and analysis of metabolic marker ions that were significantly different in immune cells from the healthy and cancer groups showed that nicotinoylglycine levels were elevated in the cancer groups of T,B,NK,and macrophages.In addition,cell proliferation assays using nicotinoylglycine and a mouse subcutaneous tumor model were performed to further investigate its biological function,which confirmed the function of nicotinoylglycine in promoting colorectal cancer tumor growth.3.Serum metabolomics of colorectal cancer based on the AOM/DSS mouse modelIn this study,an AOM/DSS mouse tumor model was established to simulate the progression of colorectal cancer from inflammation to cancer.Blood samples from each stage of the AOM/DSS model were collected for metabolomic analysis,and significant dysregulation of glycerophospholipid metabolism was found.This was consistent with the results of metabolic analysis of human plasma samples and four types of immune cells.This demonstrates the accuracy of the "whole-part" study strategy and further suggests that colorectal carcinogenesis is mainly caused by dysregulation of lipid metabolism,which provides new ideas for further screening of biomarkers for early intervention and diagnosis of colorectal cancer.