Combined MEKi and STAT3i abrogates tumorigenicity, spheroid growth, and cell invasion while enhancing apoptosis in PDAC cells. Expression of pERK and pSTAT3 in human MiaPaCa2 cells treated with MEK inhibitor (U0126) and STAT3 inhibitor (Stattic) (A) or PANC1 and MiaPaCa2 (B) cells treated with AZD6244 (MEK inhibitor) and AZD1480 (JAK/STAT3 inhibitor) in time-dependent manner for up to 24 hours. C, MiaPaCa2 cells were treated with AZD1480 with or without AZD6244 for 24 hours, stained with annexin V-FITC and propidium iodide (PI) (left panel) or PI (right panel) and analyzed by flow cytometry. Cells with AZD1480 and AZD6244 treatment resulted in an increase in apoptosis (annexin positive and PI negative) and Sub-G0 level (PI positive). D, MiaPaCa2 cells treated with the combination of AZD6244 and AZD1480 showed decreased number of colonies (left panel) and cell invasion (right panel). E, Combination of AZD1480 and AZD6244 drug treatment decreased spheroid size in MiaPaCa2 cells when compared to either control treatment or AZD1480. F, combination of AZD1480 and AZD6244 decreased spheroid size in PDXs PC-13 (left panel) and PC-17 (right panel) cells. *, P < 0.05; **, P < 0.01; ****, P < 0.0001; ns, P > 0.05.