The pancreatic cancer derived S100A8 N-terminal peptide augments intracellular Ca2+ oscillations and insulin release.

Context S100A8 N-terminal peptide (NT-S100A8) was isolated by us from pancreatic cancer (PC) tissue. Objective We verified whether NT-S100A8 alters: i) PC cell growth and invasion; and ii) insulin release and intracellular Ca2+ ([Ca2+]i) oscillations of insulin secreting cells. Methods BxPC3, Capan1, MiaPaCa2, Panc1 (human PC cell lines), beta-TC-6 (mouse insulinoma cell line). PC cell growth (trypan blue) and invasion (matrigel) were assessed in the absence (control) or presence of 50, 200 and 500 nM NT-S100A8. In control and NT-S100A8 stimulated beta-TC-6 culture medium, insulin (RIA) and Ca2+ (gas analyzer) were measured at 2, 3, 5, 10, 15, 30 and 60 minutes. [Ca2+]i oscillations of control, 50 and 500 nM NT-S100A8 stimulated beta-TC-6 was monitored (Fluo-4, epifluorescence microscopy) for three minutes. Results Five-hundred nM NT-S100A8 stimulated BxPC3 cell growth only (F=3.7, P<0.05). NT-S100A8 dose dependently enhanced Capan1 (chi-squared=16.9, P<0.01), reduced MiaPaCa2 (chi-squared=24.7, P<0.001) and Panc1 (chi-squared=16.0, P<0.05) invasion. Five-hundred nM NT-S100A8 induced a rapid (2 minutes) and persistent (further 3 minutes) insulin release (F=3.01, P<0.05). The same dosage enhanced beta-TC-6 [Ca2+]i oscillations both after one (F=6.05, P<0.01) or two minutes (F=7.42, P<0.01). The mean difference±SE between the number of [Ca2+]i spikes recorded one minute after and one minute preceding NT-S100A8 stimulation were: -0.24±0.6, 1.16±0.6, and 3.4±0.6 spikes/min for control, 50, and 500 nM stimulated cells. In the medium [Ca2+]i significantly decreased with respect to control cells (F=6.3, P<0.01). Conclusions i) NT-S100A8 exerts a mild effect on PC cell growth, while it both enhances or reduces PC cell invasion, responses being cell line specific; ii) NT-S100A8 enhances [Ca2+]i oscillations and insulin release, probably by inducing Ca2+ influx from the extracellular space.