By analogy, and given the presence of EGFR-ErbB3 heterodimers in pancreatic cancer cells, we postulated that NRG-1, a specific ErbB3 ligand, is secreted by the stroma, forms an active paracrine loop and influences response to EGFR inhibition by erlotinib. Here, NRG1 is linked to familial pancreatic carcinoma.