Fig. 4

Saa3 is a downstream effector of IL-1β that promotes the pre-metastatic niche formation and metastasis of HCC xenografts. (A) Volcano plot showing differentially expressed genes in the pre-metastatic lung of Il1b^−/− mice vs. WT mice. (B) Venn diagram showing common and exclusive genes between upregulated genes in the lung of mice implanted with Hepa1-6 vs. matrigel (Ctrl) and downregulated genes in the pre-metastatic lung of Il1b^−/− mice vs. WT mice. (C) Increased Saa3 expression in the pre-metastatic lung of HCC xenografts. (D) Decreased Saa3 expression in the pre-metastatic lung of Il1b^−/− mice. For C and D, qPCR analysis of Saa3 mRNA level was performed 2 weeks after orthotopic implantation of Hepa1-6 cells or 1 week after orthotopic implantation of H22. (E) Schematic for experimental design in F-H. Lenti-Ctrl or lenti-Saa3 viruses were given intratracheally to the lung of Il1b^−/− mice followed by orthotopic implantation of Hepa1-6 cells after 3 days. Two weeks after orthotopic implantation of Hepa1-6 cells, mice were sacrificed and IHC staining was performed. Four weeks later, tumor volume and pulmonary metastasis were detected. (F) Intratracheal administration of lenti-Saa3 viruses increased Saa3 mRNA level in the lung of Il1b^−/− mice. (G) Overexpression of Saa3 in the lung of Il1b^−/− mice increased pulmonary metastases of HCC xenografts. (H) Overexpression of Saa3 in the lung of Il1b^−/− mice increased the numbers of myeloid cells and inflammatory cells in the pre-metastatic lung. IHC staining of CD11b⁺, Ly6G⁺ and S100A9⁺ cells in the pre-metastatic lung were performed. Scale bar, 25 μm. Data are displayed as the mean ± SEM; unpaired Student’s t test (A-F). *, P < 0.05; **, P < 0.01; ***, P < 0.001