CD274 and neoplasm: Using PANC-1 cells as a model of SMAD4-intact PDAC and both BxPC-3 and AsPC-1 cells as a model of SMAD4-deficient PDAC, we next incubated tumor cells with 10ng/mL recombinant TGFβ1 for 24 hours and evaluated the expression of PD-L1 by western blot.