We observed elevated expression of PI3K, c-MYC and phosphorylation of ERK in HER2 knockdown cells than control cells, suggesting that HER3/MUC4 mediated hyperproliferation of HER2 low pancreatic cancer cells through the PI3K/ERK/c-Myc pathway. The gene discussed is ERBB2; the disease is familial pancreatic carcinoma.