SMAD4 and pachyonychia congenita: We then evaluated the expression of Smad4 in a panel of PC cell lines and found that AsPC-1, BxPC-3 and CFPAC-1 cell lines showed no Smad4 expression, while Smad4 expression was detectable in PANC-1, MIA PaCa-2 and Panc03.27 cell lines (Additional file 1: Figure S1B).