We propose that upregulation of tumor PD-L1 induced by exposure to resveratrol/piceatannol may serve to flag or sensitize the tumor cells by enhancing “tumor cell visibility” for targeting by PLB, whereas, by contrast, suppression of tumor PD-L1 by flavonoid polyphenols may act to attenuate “tumor cell visibility” thereby reducing the therapeutic dose of PLB required and, in addition, counteract the side effects of PLB. The gene discussed is CD274; the disease is neoplasm.