CD274 and neoplasm: Indeed, because of their ability to influence both the immune system and the molecular mechanisms of tumor and immune cells, polyphenols could act as modulators of the PD-1/PD-L1 system, as previously mentioned by Hsieh and M. Wu [38], and, thus, be good candidates for a combination with anti-PD-1/anti-PD-L1 with or without chemotherapy [39,40,41].