BMC Cancer 2008, 8:57 http://www.biomedcentral.com/1471-2407/8/57 80 70 IL60 T in50 140 -730 H B20 10 0 70 60 50 L I T40 + -130 D P20 10 0 A Low C P<0.0001 Medium FOXP3+ Tregs High P=0.007 Low Medium FOXP3+ Tregs High 60 50 IL40 T n i 330 P X FO20 10 0 B P=0.004 R2= 0.36 FOXP3 in TIL Predicted FOXP3 in TIL 0 20 80 100 40 60 B7-H1 in TIL CFiogrurreelat3ions between FOXP3+ Tregs, B7-H1+ TIL and PD-1+ TIL Correlations between FOXP3+ Tregs, B7-H1+ TIL and PD-1+ TIL. (A) statistical analysis of FOXP3+ Tregs infiltration in tumor tissues with B7-H1+ TIL, as analyzed with ANOVA of three groups of breast cancer patients with different FOXP3+ Tregs infiltration (Low = 0 to 4%, Medium = 5 to 14% and High 15% and above of total CD3+ TIL), (B) their linear correlation analysis and (C) statistical analysis of FOXP3+ Tregs infiltration with PD-1+ TIL in breast cancer as analyzed with ANOVA of three groups of breast cancer patients with different FOXP3+ Tregs infiltration (Low = 0 to 4%, Medium = 5 to 14% and High 15% and above of total CD3+ TIL). Discussion The immune system use intricate balance between posi- tive and negative signals to protect the body from foreign agents while preventing autoimmunity [33]. This balance seems to be disturbed in various pathological conditions resulting in either inhibition of the immune system allow- ing invasion by tumor cells, or stimulation of the immune system to cause autoimmune diseases. For example, although interaction of B7-H1, a coinhibitory molecule, with its PD-1 ligand is important for prevention of autoimmunity [34], tumor cells use this interaction as a mechanism of immune evasion [35]. Furthermore, while the presence of Tregs is important for suppression of host immune response to prevent autoimmune diseases [36], tumor cells can recruit Tregs to inhibit anti-tumor immu- nity in cancer patients [37]. We have shown previously an abundant expression of B7- H1 molecule in high-risk breast cancer patients [18] who have highly proliferative tumor cells [32] and suggested the involvement of this molecule in the progression of the disease. In the present report we expanded our study to investigate the co-involvement of Tregs with B7-H1 in the immune evasion of breast cancer. Although the interac- tion between the two types of cells has been demonstrated in vitro and animal models, their relative infiltration and correlation with the clinicopathological parameters of cancer patients have not been well studied. In this study, we investigated FOXP3+ Tregs and TIL-expressing B7-H1 and its ligand PD-1 in breast cancer patients. We have used FOXP3 as a detection marker for Tregs as it became recently a biomarker for studying Tregs in malignant human cancers [23]. We have found that FOXP3+ Tregs are Page 7 of 12 (page number not for citation purposes)