ID1 and esophageal squamous cell carcinoma: To investigate the role of Id1-induced IGF2 on VEGF-mediated tumour angiogenesis, we first compared the microvessel density in subcutaneous tumour xenografts established from KYSE150-Id1-shCON, KYSE150-Id1-shIGF2 and KYSE150-CON-shCON ESCC cells.