DEX inhibits the therapeutic effect of gemcitabine ex vivo . (A) Tumour cells from a patient (No. 1) with pancreatic cancer were freshly isolated and cultivated in a concentration of 5 × 105/ml in the absence (white bars) or presence of DEX (0.1, 1 or 10 μM as indicated) for 24 h. Gemcitabine was added (25, 50, 200 nM GEM) while the controls remained either untreated (CO) or were treated with the solvents alone (EtOH, used for dilution of DEX and DMSO, used for dilution of gemcitabine and cisplatin). 48 h after adding gemcitabine or solvents alone, viability was measured by the MTT-assay. (B) Tumour cells from patients with pancreatic cancer (No. 2-10) were freshly isolated, cultivated, and analyzed as described above. Eight wells per treatment were analyzed and standard deviations are less than 10%. Statistical analysis of significance of DEX-induced resistance is shown in Table III.