Although the upregulated genes, IFNG, GZMB and PRF1 (PRF1 encodes perforin 1), have been implicated in CD8+ T cell activation and function (30), they could be also associated with the promotion of I-MDSC suppressive function to enhance PD-L1 expression and kill reactive CD8+ T cells and favor tumor growth (31–33). Here, PRF1 is linked to neoplasm.