IGF2 and esophageal squamous cell carcinoma: Meanwhile, IGF2-activated fibroblasts or fibroblasts co-cultured with Id1-overexpressing ESCC cells were found to exert multifaceted effects on the local tumour microenvironment by inducing the proliferation, migration and tube formation (Supplementary Figs 2a–c and 3) of human umbilical vein endothelial cells, as well as increasing the invasion of ESCC cells (Supplementary Fig. 2d).