Fig. 9: EMT and SPP1 in DSS1-driven cells-related niche.

a Multiplex immunohistochemistry showing spatial distribution of DSS1-driven cells with a high epithelial-mesenchymal transition (EMT) feature (E-cad^low, Vimentin^high) around vascular cells (CD31⁺, arrows, n = 4 distinct patients). Scale bar: 40 μm. b SPP1 RNA and SPP1 protein levels in tissues of diverse cancer types (kidney cancer: RNA, n = 35 distinct cell lines, protein, n = 110 distinct samples) from the Human Protein Atlas (HPA, www.proteinatlas.org). c SPP1 Protein levels in normal tissues from the HPA database (kidney, high expression in proximal tubules, n = 3 slides). d Pseudo-bulk RNA levels of SPP1 in epithelial and immune cell types. AvgExp, Average expression. e Protein abundance of SPP1 between tumor and normal tissues in Clinical Proteomic Tumor Analysis Consortium (CPTAC)-ccRCC dataset (n = 194 distinct samples, two-tailed Mann-Whitney U test). Boxplot: Center line = median; box = 25th to 75th percentiles; whiskers = minima to maxima. f Spearman correlation between SPP1 and DSS1 mRNA expression (log₂ Count Per Million, two-tailed spearman’s rank correlation test). g Immunoblotting showing SPP1 protein levels in ccRCC cells (shDSS1 vs. shNC, n = 3 independent experiments, error bar: mean ± standard deviation [SD], two-tailed Welch’s t-test). The samples derived from the same experiment were run on parallel gels, with each gel probed for a different antibody. h Spearman correlation between CD68 expression and coexpression of SPP1-ITGB1 in spots of sample sections from either tumor core or tumor-stromal interface (Li2022 spatial dataset, n = 13 sections from 10 distinct patients; error bar: mean ± SD). i Schematic diagram (by Figdraw.com) illustrates the proposed mechanistic model of DSS1-driven cells in ccRCC metastasis: DSS1 (oligomer) interacts with pro-LC3B or LC3B-I, promoting LC3B degradation via E3 ubiquitin ligase TRIM25-mediated Lys-63 (K63)-linked polyubiquitination at LC3B-K51, leading to impaired macroautophagic flux and p62 accumulation, TWIST1 stabilization and increased TWIST1 nuclear transport, promoting EMT activation. DSS1 highly expressed (DSS1^hi) tumor cells were increased in late-stage tumors and linked to microvascular invasion within a vascularized invasive niche at the tumor-stromal interface, mediated by SPP1-ITGB1 interactions. Statistics are provided in the source data. Source data are provided as a Source Data file.