Fig. 1

Spermine promotes tumor growth and metastasis through inducing PD-L1 expression in HCC. A Blood spermine was determined with HPLC in 24 normal subjects and 24 HCC patients. ***p < 0.001, two-tailed unpaired t test. B Spearman correlation test between blood spermine level and tumor PD-L1 IHC scores. Left: Representative images of IHC staining. Scale bar, 50 µm. Right: Correlation analysis. Note that some of the dots represent more than one specimen. C Spearman correlation test between blood spermine level and tumoral CD8⁺ T-cell infiltration. Left: Representative images of IHC staining from 24 human HCC specimens. Scale bar, 50 µm. Right: Correlation analysis. D, E Effects of spermine on the expression of CD274 mRNA (D) and PD-L1 protein (E) in HCC cells (SNU-368, SNU-739, Huh-7 and HepG2). *p < 0.05, **p < 0.01, ***p < 0.001 compared with control group, one-way ANOVA, n = 5 independent experiments per group. F, G IHC staining of tumoral PD-L1 (F) and CD8α (G) from tumor-grafted mice received with or without spermine treatment. Tumor-grafted mice was constructed with H22 tumor cells transfected with or without Ctrl shRNA or shPD-L1. Left: Representative images. Scale bar, 50 µm. Right: Correlation analysis. *p < 0.05, **p < 0.01, ***p < 0.001, one-way ANOVA, n = 8 mice per group. H Representative images of tumors and quantification of tumor weight collected from tumor-grafted mice received with or without spermine treatment. Tumor-grafted mice was constructed with H22 tumor cells transfected with or without Ctrl shRNA or shPD-L1. ***p < 0.001, one-way ANOVA, n = 8 mice per group. I Representative photos of metastatic lung nodules and quantification of the lung nodules from tumor-grafted mice received with or without spermine treatment. **p < 0.01, ***p < 0.001, one-way ANOVA, n = 8 mice per group