CD8+ T cell densities and PD-L1 associated with favorable prognosis in schistosomiasis-associated Colorectal Cancer

Backgroud: The expression of programmed cell death-ligand 1 (PD-L1) was correlated with CD8+ T cells, which could producing IFNγ. The effect of infection of Schistosoma japonicum on CD8+ tumour-infiltrating lymphocytes (TILs) and then on PD-L1 expression has rarely been reported and the utility of CD8+ TILs as a biomarker for colorectal cancer (CRC), especially for schistosomal CRC, are still controversial and needing to be determined in CRC. Methods: : A total of 338 patients with CRC were enrolled in this study. Immunohistochemical analysis were performed to evaluated the expression of PD-L1 within tumor cells (tPD-L1) and within stromal cells (sPD-L1), infiltration by CD8+ T cells. Results: : In the whole cohort, results showed that CD8 + TIL density was positively correlated with tumoral and stromal PD-L1 expression （ p ＜0.05）. But there were no correlation between schistosomiasis and PD-L1 and CD8+ TILs. Furthermore, CD8 + TIL density, schistosomiasis, TNM stage, lymph nodes positive for CRC and gender were significantly independent predictive factors for overall survival (OS)（ p ＜0.05）. Stromal PD-L1 but not tPD-L1 expression was correlated with OS but was not an independent predictor ( p=0.046 ). In patients without schistosomiasis, sPD-L1 was significantly associated with better OS but was not an independent predictor（ p =0.004 ）.However, there were no association between schistosomiasis and OS in patients with schistosomal ifection. Conclusions: : Our analysis indicated that CD8 + was an independent predictive factor for OS. And the expression of PD-L1 was positively associated with CD8+ TILs density. There were no correlation between schistosomiasis and PD-L1 and CD8+ TILs. Stromal PD-L1 but not tPD-L1 was significantly associated with OS, but was not an independent prognostic factor. It is proposed that PD-L1 expression in combination with CD8 + TIL could be a useful predictive biomarker in CRC patients.