To assess the downstream effect of transligation between aT-sEV PD-1/CD80 and tumour cell PD-L1, we then evaluated the expression level of tumour PD-L1 following aT-sEV treatment in a panel of tumour cell lines, including human oral cancer, melanoma, breast cancer and lung cancer cell lines. The gene discussed is PDCD1; the disease is lip and oral cavity carcinoma.