Fig. 1: Correlation of S1P1 expression with numbers of Foxp3⁺ Tregs in tumor specimens from BC patients.

a Gating strategy for the assessment of the Treg population by flow cytometry. The CD4⁺ cells were gated from live PBMCs or TILs, and the CD4⁺Foxp3⁺ cells were further gated as Tregs. b A statistical analysis revealed that the percentage of Treg cells in the population of TILs (n = 60) was significantly higher compared with that in the population of PBMCs (n = 87) from BC patients (P < 0.01), whereas the percentage of Tregs in the population of PBMCs (n = 87) from BC patients was significantly higher than that in the PBMCs from healthy donors (P < 0.01, n = 31). c Representative IHC staining for Foxp3 and S1P1 in tumor and tumor-adjacent tissues from BC patients. d Statistical analysis of the levels of tumor-infiltrated Foxp3⁺ cells and S1P1 in tumor tissues and tumor-adjacent tissues from the same patient (P < 0.05; n = 17 or 21, respectively). e Pearson’s correlation coefficient and linear regression array for the correlation of the number of tumor-infiltrated Foxp3⁺ cells and the tumor S1P1 expression level (R = 0.196, P = 0.035). f Immunoblotting analysis of the levels of S1P1 in tumor tissues obtained from BC patients with high numbers of tumor-infiltrating Foxp3⁺ cells and BC patients with lower numbers of tumor-infiltrating Foxp3⁺ cells. IHC, immunohistochemical staining; R, Spearman’s correlation; P, significance of the correlation