While PD-1 / PD-L1 blockade showed only marginal efficacy in this setting paralleling results of clinical trials with PD-1/PD-L1 blockade in MSS CRC, impressive effects were achieved when PD-1/PD-L1 blockade was combined with inhibition of transforming growth factor beta (TGF-β) [27]. This evidence concerns the gene PDCD1 and colorectal carcinoma.