SPON2 promotes glioma invasion and pro-angiogenic activity with involvement of ITGA5-related integrin signaling and β-catenin/TCF transcriptional activity

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Abstract Purpose Glioma is a highly aggressive primary brain tumor characterized by infiltrative growth, vascular abnormalities, and poor clinical outcome. However, extracellular matrix-associated regulators that contribute to glioma progression remain incompletely understood. This study aimed to determine the expression, biological function, and potential molecular mechanism of SPON2 in glioma. Methods Differential expression, survival, WHO grade, IDH status, and adjusted survival analyses were performed using public glioma datasets. SPON2 expression was validated in the Rembrandt, TCGA, and CGGA cohorts, as well as in glioma tissue microarrays and cell lines. Gain- and loss-of-function experiments, xenograft assays, RNA sequencing, qRT-PCR validation, immunofluorescence, Western blotting, TOPFlash/FOPFlash reporter assays, GST pull-down assays, and co-immunoprecipitation were used to investigate the role of SPON2 and the relationships among SPON2, ITGA5/ITGB1-containing integrin complexes, and β-catenin/TCF transcriptional activity. Results SPON2 was upregulated in glioma, increased with WHO grade, and was enriched in IDH-wildtype tumors. SPON2 knockdown suppressed glioma cell invasion, migration, and pro-angiogenic activity, whereas SPON2 overexpression enhanced these malignant phenotypes. In vivo, stable SPON2 knockdown inhibited xenograft growth and reduced angiogenesis-related features. RNA-seq linked SPON2 to Wnt-related signaling, ECM-receptor interaction, and focal adhesion pathways, and selected RNA-seq-associated genes were validated in independent glioma cell models. SPON2 modulation altered nuclear β-catenin accumulation, β-catenin/TCF reporter activity, and the expression of AXIN2, CCND1, c-MYC, MMP-2, MMP-9, and VEGF. GST pull-down, co-immunoprecipitation, and colocalization analyses supported an association between SPON2 and ITGA5/ITGB1-containing integrin complexes, while ITGA5 knockdown attenuated SPON2-associated β-catenin/TCF transcriptional activity and malignant phenotypes. Conclusion These findings support a pro-malignant role of SPON2 in glioma and indicate that ITGA5-related integrin signaling and β-catenin/TCF transcriptional activity participate in SPON2-associated malignant phenotypes. SPON2 may represent a candidate marker associated with aggressive glioma features and warrants further mechanistic investigation.