In-Depth Proteomic Analysis of Tissue Interstitial Fluid Reveals Biomarker Candidates Related to Varying Differentiation Statuses in Gastric Adenocarcinoma

The proteomic heterogeneity of gastric adenocarcinoma
(GC) has
been extensively investigated at the bulk tissue level, which can
only provide an average molecular state. In this study, we collected
an in-depth quantitative proteomic dataset of tissues and interstitial
fluids (ISFs) from both poorly and non-poorly differentiated GC and
presented a comprehensive analysis from several perspectives. Comparison
of proteomes between ISFs and tissues revealed that ISF exhibited
higher abundances of proteins associated with blood microparticles,
protein–lipid complexes, immunoglobulin complexes, and high-density
lipoprotein particles. Also, consistent and inconsistent protein abundance
changes between them were revealed by a correlation analysis. Interestingly,
a more pronounced difference between tumors and normal adjacent tissues
was found at the ISF level, which accurately reflected tissue properties
compared to those of bulk tissue. Two ISF-derived biomarker candidates,
calsyntenin-1 (CLSTN1) and prosaposin (PSAP), were identified by distinguishing
patients with different differentiation statuses and were further
validated in serum samples. Additionally, the silencing of CLSTN1
and PSAP was demonstrated to suppress cell proliferation, migration,
and invasion in poorly differentiated gastric cancer cell lines. In
summary, the ISF proteome offers a new perspective on tumor biology.
This study provides a valuable resource that significantly enhances
the understanding of GC and may ultimately benefit clinical practice.

胃腺癌（gastric adenocarcinoma, GC）的蛋白质组异质性已在大块组织层面得到广泛研究，但此类研究仅能反映整体的平均分子状态。本研究收集了低分化与非低分化胃腺癌患者的组织及组织间液（interstitial fluids, ISFs）的深度定量蛋白质组数据集，并从多个维度开展了全面分析。通过对比组织间液与组织的蛋白质组，发现组织间液中与血液微粒、蛋白-脂质复合物、免疫球蛋白复合物及高密度脂蛋白颗粒相关的蛋白丰度显著更高。相关性分析进一步揭示了二者间蛋白丰度变化的一致性与不一致性。有趣的是，在组织间液层面，肿瘤与癌旁正常组织间的差异更为显著，相较于大块组织层面的分析结果，该差异更能准确反映组织的真实特性。本研究通过区分不同分化状态的患者，筛选出两种源自组织间液的候选生物标志物：钙连蛋白-1（CLSTN1）与prosaposin（PSAP），并在血清样本中完成了验证。此外，实验证实沉默CLSTN1与PSAP可抑制低分化胃癌细胞系的细胞增殖、迁移与侵袭能力。综上，组织间液蛋白质组为肿瘤生物学研究提供了全新视角。本研究构建了极具价值的数据集资源，显著加深了学界对胃腺癌的认知，最终有望惠及临床实践。