VAV2 and esophageal squamous cell carcinoma: These in vitro results indicate that Fludarabine may assist IR to kill radioresistant ESCC cells overexpressing VAV2, which were confirmed by the assays in vivo in mouse xenografts derived from KYSE150 overexpressing VAV2 (Supplementary Fig. S7d) or radioresistant PDC-5 cells (Fig. 5j and Supplementary Fig. S7e).