Cell viability

An MTT assay was used to measure cell viability according to the manufacturer's protocol. Cells were plated at a density of 5×104/well into 96-well plates and treated with Beclin 1, Beclin 1 + XAV939 or Beclin 1 + wnt3α for 24 h, and then stimulated with 20, 40 or 60 µg/ml Gemcitabine for 2 days. Subsequently, 10 µl MTT solution (5 mg/ml; Sigma-Aldrich; Merck KGaA) was added to each well and cells were incubated at 37°C for 4–6 h. Formazan crystals dissolved in 150 µl DMSO were added for 10 min with agitation. Absorbance was measured at a wavelength of 490 nm using a microplate reader (Bio-Rad Laboratories, Inc., Hercules, CA, USA).