CD274 and neoplasm: Recently, viruses, especially Epstein–Barr virus (EBV) ((Wang et al. 2022), human papillomavirus (HPV) ((Ling et al. 2022), and hepatitis B virus (HBV) ((Jia et al. 2024)have been shown to upregulate PD-L1 expression, suppress T-cell activity, and promote immune tolerance, facilitating tumor immune escape.