A Plasma Metabolomic Analysis Of Extrahepatic Cholangiocarcinoma For Diagnosis And Biomarker Discovery

Cholangiocarcinoma(CC) accounts for about3%of all gastrointestinal malignancies;however, it represents the second most common hepatic malignancy after hepatocellularcarcinoma. Hilar cholangiocarcinomas,the most common types of extrahepaticcholangiocarcinomas(EHCCs), represent60–70%of all CCs, whereas intrahepatic tumorsrepresent5–10%and distal extrahepatic tumors20–30%. There are many risk factorsleading to CCs, however, the majority of patients had no clear risk factors. The specificmolecular mechanisms leading to CCs are not clear so far.If we find information about themolecular mechanisms and molecules involved in the change, it will be of importantguiding significance to early diagnosis, treatment and prognosis of CCs. Current diagnosticmethods are unlikely for the early diagnosis of EHCCs. It is more difficult to the diagnosisof hilar CCs than the distal because of the special anatomic structure of hilar. Therefore,the diagnosis of EHCCs is very difficult, especially in terms of the identification withbenign diseases. New diagnostic methods are necessary.Metabolomics is a method for quantitative analysis of metabolites in vivo, trying tofind the relative relationship between metabolites and the physiological and pathologicalchanges. Metabolomics could be applied to the study of various body fluids such as blood,urine, bile, saliva, etc., especially for the tissues and organs that store and produce smallmolecule metabolites. Metabolomics showed some good diagnostic effects of somecarcinomas, such as breast carcinoma, ovarian carcinoma, prostate carcinoma.Objective: The metabolomics study will analyze the plasma of the patients of EHCC,primary choledocholithiasis and choledochal cyst and the plasma of the healthy individualsby gas chromatography-mass spectrometry(GC-MS) to clarify the characteristic changes ineach group, and compared with the existing CC tumor markers, we will initially identifymolecules in peripheral blood for the early diagnosis of EHCC.Methods: Plasma samples were collected from patients with EHCC(n=54), primarycholedocholithiasis(n=20) and choledochal cyst(n=23) as well as the healthy individuals(n=22). Small molecules in plasma metabolites were detected by GC-MS. GC-MS data ofthese blood samples were analyzed using principal component analysis, partial leastsquares discrimination analysis and orthogonal partial least squares discrimination analysis to create a model of differential diagnosis and screen the significant markers. The analysisresults were compared with the commonly used tumor markers.Results: According to the multivariate statistical analysis data, we initially established thedifferential diagnosis model of plasma metabolomics among EHCC, primarycholedocholithiasis, choledochal cyst and healthy individuals. We identified two specificplasma metabolites in EHCC, D-galacturonic acid and cis-2-hydroxycinnamic acid.D-galacturonic acid in EHCC group was significantly higher than the healthy control group,choledochal cyst group and primary choledocholithiasis group(P<0.05).Cis-2-hydroxycinnamic acid in EHCC group was significantly lower than the healthycontrol group, choledochal cyst group and primary choledocholithiasis group(P<0.05).Both have shown a high sensitivity and specificity in the diagnosis of EHCC.Conclusions: Combined with multivariate statistical methods, we found metabolomicstechnology could provide a new method for the diagnosis of EHCC and a new way for thestudy of the pathogenesis, and provided new ideas for further clinical treatment.