CD274 and neoplasm: Predictive biomarkers such as PD-L1 expression (on tumor or immune cells), high microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR), and high tumor mutational burden (TMB) are surrogates for an inflamed TME likely containing neoantigens and potentially reactive, albeit suppressed, T cell populations (Ma et al., 2022).