OBJECTIVES We aimed to identify serum level variations in protein-derived peptides between patients diagnosed with gastric adenocarcinoma (GAC) and non-cancer persons (control) to detect the activity changes of proteases and explore the auxiliary diagnostic value in the context of GAC physiopathology. METHODS The label-free quantitative peptidome approach was applied to identify variants in serum levels of peptides that can differentiate GAC patients from the control group. Peptide sequences were submitted against Proteasix tool predicting proteases potentially involved in their generation. The activity change of proteases was subsequently estimated based on the peptides with significantly altered relative abundance. In turn, activity change prediction of proteases was correlated with relevant protease expression data from the literature. RESULTS A total of 191 peptide sequences generated by the cleavage of 36 precursor proteins were identified. Using the label-free quantification approach, 33 peptides were differentially quantified (adjusted fold change ≥ 1.5 and p-value < 0.05) in which 19 were up-regulated and 14 were down-regulated in GAC samples. Of these peptides, fibrinopeptide A was significantly decreased and its phosphorylated form ADpSGEGDFLAEGGGVR was upregulated in GAC samples. Activity change prediction yielded 10 proteases including 6 Matrix Metalloproteinases (MMPs), Thrombin, Plasmin, and kallikreins 4 and 14. Among predicted proteases in our analysis, MMP-7 was presented as a more promising biomarker associated with useful assays of clinical practice for GAC diagnosis. CONCLUSION Our experimental results demonstrate that the serum levels of peptides were significantly differentiated in GAC physiopathology. The hypotheses built on protease regulation could be used for further investigations to measure proteases and their activity levels that have been poorly studied for GAC diagnosis.

中文翻译：

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无标记肽定量结合蛋白酶的计算机绘图，用于鉴定胃腺癌患者潜在的血清生物标志物。

目的我们旨在确定诊断为胃腺癌（GAC）的患者和非癌症患者（对照）之间的蛋白衍生肽的血清水平变化，以检测蛋白酶的活性变化并探讨在GAC生理病理学背景下的辅助诊断价值。方法采用无标记的定量肽组方法来鉴定血清水平的多肽变体，该变体可以使GAC患者与对照组区别开来。针对Proteasix工具提交了肽序列，该工具预测了可能参与其生成的蛋白酶。随后根据相对丰度发生明显变化的肽段评估蛋白酶的活性变化。反过来，蛋白酶的活性变化预测与文献中相关的蛋白酶表达数据相关。结果鉴定出通过切割36种前体蛋白产生的总共191个肽序列。使用无标记定量方法，对GAC样品中的33种肽进行了差异定量（调整的倍数变化≥1.5，p值<0.05），其中19种上调而14种下调。在这些肽中，GAC样品中的纤维蛋白肽A显着减少，其磷酸化形式ADpSGEGDFLAEGGGVR。预测活性变化可产生10种蛋白酶，包括6种基质金属蛋白酶（MMP），凝血酶，纤溶酶和激肽释放酶4和14。在我们的预测预测蛋白酶中，MMP-7被认为是一种更有前途的生物标志物，与GAC临床实践的有用检测有关诊断。结论我们的实验结果表明，在GAC生理病理学中，血清中的肽水平显着不同。基于蛋白酶调节的假说可用于进一步研究，以测量蛋白酶及其活性水平，而对于GAC诊断，蛋白酶及其活性水平研究不足。