PECAM1 and cancer: F4/80+ tumour-associated macrophages (TAMs), α-smooth muscle actin (αSMA)+ cancer-associated fibroblasts (CAFs), CD3+ lymphocytes and CD31+ tumour endothelial cells were negative for IL-33 (Supplementary Figure 5a), and IL-33 was detected in some EGFP-positive cells in EGFP-P29 tumours (Supplementary Figure 5b).