Tumor-Derived Exosomal PDLIM1 Promotes Angiogenesis and Tumor Progression in Papillary Thyroid Carcinoma: Insights From Integrated Single-Cell Transcriptomics and Exosomal Proteomics

Background: Papillary thyroid carcinoma (PTC) with metastatic potential presents a complex and poorly understood tumor microenvironment. Despite its clinical significance, the cellular and molecular mechanisms driving metastatic progression remain inadequately characterized, particularly the role of intercellular communication mediated by tumor-derived exosomes. Methods: We analyzed single-cell RNA sequencing (scRNA-seq) on primary and metastatic PTC tissues (n=12 samples from 4 patients), exploring cellular heterogeneity and distinct subpopulations. Metastasis-associated cell states (Scissor+ and Scissor-) were delineated using the Scissor algorithm. Pathway activity in these subpopulations was analyzed using the PROGENy algorithm.Exosomal proteomic data from lymph node metastasis patients were cross-referenced with Scissor+ signatures, identifying candidate proteins. Functional validation included in vitro angiogenesis assays with HUVECs and in vivo xenograft models to assess tumor growth and vascularization. Results: ScRNA-seq revealed significant tumor cell heterogeneity between primary and metastatic sites, with Scissor+ cells strongly linked to metastatic phenotypes. PROGENy analysis demonstrated significant upregulation of VEGF signaling in Scissor+ cells. Among six key proteins identified, PDLIM1 was highly expressed in PTC cell lines and metastatic tissues (P < 0.001). Tumor-derived exosomal PDLIM1 was internalized by endothelial cells, enhancing angiogenesis in vitro. PDLIM1 knockdown in exosomes suppressed HUVEC tube formation (P < 0.05) and reduced tumor volume, CD31+ microvessel density, and LYVE-1+ lymphatic vessel density in xenografts (P < 0.05). Conclusion: Our study suggests that exosomal PDLIM1 may play a role in promoting angiogenesis and primary tumor progression in PTC. These findings provide preliminary insights into the potential involvement of exosome-mediated intercellular communication in PTC pathogenesis. Further validation in larger cohorts and functional studies, including rescue experiments, are warranted to evaluate whether targeting PDLIM1 could represent a viable therapeutic strategy. Keywords: papillary thyroid carcinoma, exosomal proteomics, single-cell transcriptomics, angiogenesis, PDLIM1