血浆外泌体中的CD48蛋白作为潜在的肝细胞癌诊断标志物的研究

背景与目的：约60%的肝细胞癌（hepatocellular carcinoma，HCC）患者在晚期才被确诊，因而无法得到及时有效的治疗，目前临床上常用于HCC诊断的血清标志物的灵敏度均偏低。本研究通过分析血浆外泌体蛋白质组的表达差异，鉴定可能用于HCC诊断的候选外泌体蛋白质标志物。方法：首先，采用鸟枪法蛋白质组质谱分析方法，对发掘人群包括4名健康对照者（healthy control，HC）组和4例HCC患者组]的血浆外泌体进行全蛋白质组的定性和定量分析，并筛选差异表达蛋白质。然后，采用酶联免疫吸附试验（enzyme-linked immunosorbent assay，ELISA）在独立的验证人群包括56例HCC患者组、20例肝硬化（liver cirrhosis，LC）患者组和48名HC组]中进行验证实验，并评估候选蛋白质分子在HCC诊断中的潜在价值。结果：在发掘人群中，共鉴定到1 434种血浆外泌体蛋白质，其中的CD48蛋白在HCC患者中的表达水平显著高于HC组个体。进一步采用ELISA在独立验证人群中证实CD48蛋白在HCC患者中的表达水平显著高于LC和HC个体，受试者工作特征（receiver operating characteristic，ROC）曲线的曲线下面积（area under curve，AUC）为0.886。当联合检测血浆外泌体中的CD48蛋白和血浆中的甲胎蛋白（alpha-fetoprotein，AFP）时，AUC可提升至0.970。结论：血浆外泌体中的CD48蛋白可能作为HCC的候选诊断标志物，当其与AFP联合应用时可能进一步提高HCC的临床诊断能力。

Plasma exosomal CD48 protein as a candidate diagnostic biomarker for hepatocellular carcinoma

Background and purpose: Approximately 60% of patients with hepatocellular carcinoma (HCC) are diagnosed at an advanced stage, therefore cannot receive timely and effective treatment. At present, the sensitivity of serum biomarkers commonly used in the diagnosis of HCC is low. In this paper, through the differential expression analysis of plasma exosomal proteome, the candidate exosome protein markers which may be used in the diagnosis of HCC were identified. Methods: First, we performed shot-gun proteome mass spectrometry assays in the plasma exosomes from the discovery cohort including 4 healthy control (HC) group and 4 HCC patients group], and identified differentially expressed proteins by qualitative and quantitative analyses. Then, we carried out enzyme-linked immunosorbent assay (ELISA) in plasma samples of an independent verification cohort including 56 HCC patients group, 20 liver cirrhosis (LC) patients group and 48 HC group], and evaluated the diagnostic value of the candidate protein in HCC. Results: In the discovery cohort, we identified a total of 1 434 exosomal proteins, of which CD48 exhibited higher levels in HCC than in HC. We further verified in the validation cohort by ELISA that CD48 was markedly higher in HCC compared with LC and HC groups, with the area under receiver operating characteristic (ROC) curve (AUC) of 0.886. When combined with plasma alpha-fetoprotein (AFP), the AUC reached 0.970. Conclusion: The plasma exosomal CD48 protein can be used as a candidate diagnostic biomarker for HCC, and its combination with AFP may further improve the clinical diagnostic ability for HCC.