Among all the detected ligands on BMFs and tumor cells after co-culture conditions, only the BMFs after the co-culture with tumor cells exhibited significantly upregulated expression level of PD-L1 (Figures 2A, B, Supplementary Figure 3), implying that the induction of PD-L1 on BMFs by cancer cells could account for the aPD-L1 therapy resistance in BMF-mixed xenografts. This evidence concerns the gene CD274 and neoplasm.