PDCD1 and central nervous system cancer: The better prognosis of patients with simultaneous low expression of TGFBR1 and PD-L1 is in some agreement with the above-mentioned studies, making the combination of TGF-β1/TGFBR1 inhibitors and PD-1/PD-L1 inhibitors a potential immunotherapeutic strategy for glioma (160).