We infected A549 lung cancer cells and MCF7 breast cancer cells with a lentivirus encoding ephrin-B2 fused to EGFP and first examined the effects on endogenous EphB4, which binds the ephrin-B2 ligand in trans. Like EphA2, EphB4 is widely expressed in cancer cells [1,30] and its ability to be regulated by ephrins in cis was not previously examined. Here, EPHA2 is linked to breast carcinoma.