In spite of the obvious evidence that high HER3 expression in pancreatic cancer cells and NSCLC cells confers increased sensitivity to gefitinib or erlotinib than in low HER3-expressing cells [89], the above resistance promoting function may be caused by an increase in the level of activated HER3 rather than of total HER3 protein expression. Here, ERBB3 is linked to familial pancreatic carcinoma.