VAV2 and esophageal squamous cell carcinoma: To test this notion, we treated ESCC cell lines or radiosensitive primary ESCC cells (PDC-2 from PDX-2) having ectopic VAV2 overexpression and radioresistant primary ESCC cells (PDC-5 from PDX-5) having forced VAV2 silence with IR and found that cells overexpressing VAV2 were not or much less sensitive to IR compared with cells without VAV2 overexpression (Fig. 2a, b and Supplementary Fig. S2c–f); in contrast, silencing VAV2 expression in primary radioresistant ESCC cells re-conferred sensitivity to IR (Fig. 2c and Supplementary Fig. S2g, h).