TGFA and colon carcinoma: Immortalized cell line SW620, deriving from a human lymph node metastasis from an adenocarcinoma of the colon [27], was selected from a colon carcinoma library [28] for its very low EGFR expression (electronic supplementary material, figures S1 and S2) consistent with previous recent findings [29–32] and low expression of the most common EGFR ligands, including TGFA.