Helicobacter pylori (H. pylori) upregulates PD-L1 in gastric cancer cells via CagA-dependent SHH signaling [81, 82], and Porphyromonas gingivalis upregulates PD-L1 in prostate cancer via the IRAK/NF-κB pathway [83] (Fig. 3). The gene discussed is CD274; the disease is gastric cancer.