Fig. 2

Colony-forming assay. a Cytostatic and cytotoxic analysis of colonies in BxPC-3 (left panel), CFPAC-1 (middle panel), and Panc-1 (right panel). Upper panel represents the effect of 72 h IFN-β monotherapy on surviving fraction and colony size. Middle and lower panel represent the effect of 72 h gemcitabine (GEM) in untreated control cells (white bar) versus 72 h IFN-β pre-treated cells (black bar) on surviving fraction and colony size. Used concentrations IFN-β: 100 IU/ml for BxPC-3 and CFPAC-1, and 1000 IU/ml for Panc-1. Used concentrations gemcitabine: 0.5–1 ng/ml for CFPAC-1; and 1–2.5 ng/ml for BxCP-3 and Panc-1. Data are presented as percentage of vehicle treated control. For IFN-β pre-treated cells, effect of IFN-β was set on 100% and used as control. b Photomicrographs of treatment effects on BxPC-3 colonies. Red stained colonies represent the measured colonies. Based on cut-off values for number and size, black stained colonies were excluded. Values represent mean ± SEM of at least two independent experiments and are shown as a percentage of control. *p < 0.05, **p < 0.01, and ***p < 0.001 versus control