CD274 and cancer: RT2.Stat1+/+-cancers and RT2.Stat1−/−-cancers had normal baseline levels of PD-L1 and β2-microglobulin, and in RT2.Stat1−/−-cancers β2-microglobulin was in the tumour microenvironment (Supplementary Fig. 4a–d and Supplementary Fig. 8d).