Fig. 3. Metformin potently inhibits DNA synthesis and proliferation in PDAC cells incubated in 5 mM glucose.

A) Dose-response effect of metformin on DNA synthesis induced by neurotensin and insulin in MiaPaca-2 cells. Cultures in serum-free medium containing 5mM (closed circles) or 25 mM glucose (open circles) were stimulated with 5 nM neurotensin and 10 ng/ml insulin in the presence of metformin (0.025–1 mM). Results are expressed as the percentage of maximum mean ±SEM, n=6. B) Effect of metformin on DNA synthesis induced by IGF in hTERT-HPNE cells. The hTERT-HPNE cell cultures were stimulated with 10 ng/ml IGF-1 in the absence or presence of 1mM metformin (as indicated). Results are expressed as the percentage of maximum mean ±SEM; n=6. C) Low concentrations of metformin inhibit DNA synthesis in MiaPaca-2 and PANC-1 cells cultured in DMEM containing 5 mM glucose. Cultures were incubated in medium containing 5mM glucose either in the absence (grey bars) or the presence of 0.05 mM or 0.1 mM metformin (black bars) and 5nM neurotensin and 10 ng/ml insulin (NT + Ins) as indicated. Results are expressed as the percentage of maximum mean ±SEM, n=6. D), Low concentrations of metformin inhibit proliferation of MiaPaca-2 and PANC-1 cells cultured in DMEM containing 5 mM glucose. Single-cell suspensions of MiaPaca-2 and PANC-1 cells were plated at a density of 2 × 10⁴ cells per dish. After 4 h, the cultures were shifted to media containing 1% FBS without (−) or with 10 nM neurotensin and 10 ng/ml insulin (NT + Ins) the absence (grey bars) or presence (closed bars) of 0.05 mM or 0.1 mM metformin. After 4 days, cell numbers were determined from 6 plates per condition. Results are presented as mean ± SEM. Similar results were obtained in two independent experiments. P values were determined using the t-test (SigmaPlot 12.) *p<0.05; **p<0.01; n=6.