To identify the cellular source of ECM/stromal gene signature, we applied our previously developed multiparametric flow cytometric profiling strategy in resected tumours from a larger cohort of human NSCLC patients for the presence of mesenchymal cells based on the expression of CD90 and CD73 and their coexpression of PD-L1 and the innate checkpoint molecule CD47 (Fig. S4a,b).27 Here, CD274 is linked to non-small cell lung carcinoma.