Background Esophageal cancer (EC) is one of the malignant tumors with a poor prognosis. The early stage of EC is asymptomatic, so identification of cancer biomarkers is important for early detection and clinical practice. Methods In this study, we compared the protein expression profiles in esophageal squamous cell carcinoma (ESCC) tissues and adjacent normal esophageal tissues from five patients through high-resolution label-free mass spectrometry. Through bioinformatics analysis, we found the differentially expressed proteins of ESCC. To perform the rapid identification of biomarkers, we adopted a high-throughput protein identification technique of Quantitative Dot Blot (QDB). Meanwhile, the QDB results were verified by classical immunohistochemistry. Results In total 2297 proteins were identified, out of which 308 proteins were differentially expressed between ESCC tissues and normal tissues. By bioinformatics analysis, the four up-regulated proteins (PTMA, PAK2, PPP1CA, HMGB2) and the five down-regulated proteins (Caveolin, Integrin beta-1, Collagen alpha-2(VI), Leiomodin-1 and Vinculin) were selected and validated in ESCC by Western Blot. Furthermore, we performed the QDB and IHC analysis in 64 patients and 117 patients, respectively. The PTMA expression was up-regulated gradually along the progression of ESCC, and the PTMA expression ratio between tumor and adjacent normal tissue was significantly increased along with the progression. Therefore, we suggest that PTMA might be a potential candidate biomarker for ESCC. Conclusion In this study, label-free quantitative proteomics combined with QDB revealed that PTMA expression was up-regulated in ESCC tissues, and PTMA might be a potential candidate for ESCC. Since Western Blot cannot achieve rapid and high-throughput screening of mass spectrometry results, the emergence of QDB meets this demand and provides an effective method for the identification of biomarkers.

中文翻译：

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通过无标记定量蛋白质组学和定量斑点印迹 (QDB) 鉴定胸腺肽原 (PTMA) 作为食管鳞状细胞癌 (ESCC) 的生物标志物。

背景食管癌（EC）是预后较差的恶性肿瘤之一。EC的早期无症状，因此癌症生物标志物的识别对于早期发现和临床实践非常重要。方法 在这项研究中，我们通过高分辨率无标记质谱法比较了来自 5 名患者的食管鳞状细胞癌 (ESCC) 组织和邻近的正常食管组织中的蛋白质表达谱。通过生物信息学分析，我们发现了ESCC的差异表达蛋白。为了进行生物标志物的快速鉴定，我们采用了定量点印迹（QDB）的高通量蛋白质鉴定技术。同时，QDB结果通过经典免疫组织化学验证。结果 共鉴定出 2297 种蛋白质，其中 308 种蛋白质在 ESCC 组织和正常组织之间差异表达。通过生物信息学分析，选择了四种上调蛋白（PTMA、PAK2、PPP1CA、HMGB2）和五种下调蛋白（Caveolin、Integrin beta-1、Collagen alpha-2(VI)、Leiomodin-1 和 Vinculin）并通过 Western Blot 在 ESCC 中验证。此外，我们分别对 64 名患者和 117 名患者进行了 QDB 和 IHC 分析。PTMA的表达随着ESCC的进展逐渐上调，肿瘤与癌旁正常组织间的PTMA表达比例也随着进展而显着升高。因此，我们建议 PTMA 可能是 ESCC 的潜在候选生物标志物。结论 在这项研究中，无标记定量蛋白质组学结合 QDB 显示 PTMA 在 ESCC 组织中表达上调，PTMA 可能是 ESCC 的潜在候选者。由于Western Blot无法实现对质谱结果的快速、高通量筛选，QDB的出现满足了这一需求，为生物标志物的鉴定提供了有效的方法。