SMAD4 and pancreatic neoplasm: Consequently, AsPC-1 and MIA PaCa-2 cells were chosen as in vitro models because of their resistant and sensitive responses to gemcitabine with deficient and sufficient SMAD4 expression, as well as mutant/wild-type genetic status, respectively, to further test the hypothesis that SMAD4 might play a key role in chemoresistance of pancreatic cancer.