PDCD1 and gastric cancer: By analyzing the circRNA expression profiles in primary and paired distant metastatic gastric cancer tissues as well as tissues that respond to or are resistant to anti-PD-1 therapy, we found that circDLG1 (circRNA ID: hsa_circ_0008583) was upregulated in distant metastatic lesions and tissues resistant to anti-PD-1 therapy, and high circDLG1 expression was associated with worse PFS in gastric cancer patients treated with anti-PD-1 therapy.