Altered intracellular calcium fluxes in pancreatic cancer induced diabetes mellitus: Relevance of the S100A8 N‐terminal peptide (NT‐S100A8)

Abstract

After isolating NT-S100A8 from pancreatic cancer (PC) tissue of diabetic patients, we verified whether this peptide alters PC cell growth and invasion and/or insulin release and [Ca(2+)](i) oscillations of insulin secreting cells and/or insulin signaling. BxPC3, Capan1, MiaPaCa2, Panc1 (PC cell lines) cell growth, and invasion were assessed in the absence or presence of 50, 200, and 500 nM NT-S100A8. In NT-S100A8 stimulated β-TC6 (insulinoma cell line) culture medium, insulin and [Ca(2+)] were measured at 2, 3, 5, 10, 15, 30, and 60 min, and [Ca(2+)](i) oscillations were monitored (epifluorescence) for 3 min. Five hundred nanomolars NT-S100A8 stimulated BxPC3 cell growth only and dose dependently reduced MiaPaCa2 and Panc1 invasion. Five hundred nanomolars NT-S100A8 induced a rapid insulin release and enhanced β-TC6 [Ca(2+)](i) oscillations after both one (F = 6.05, P < 0.01) and 2 min (F = 7.42, P < 0.01). In the presence of NT-S100A8, [Ca(2+)] in β-TC6 culture medium significantly decreased with respect to control cells (F = 6.3, P < 0.01). NT-S100A8 did not counteract insulin induced phosphorylation of the insulin receptor, Akt and IκB-α, but it independently activated Akt and NF-κB signaling in PC cells. In conclusion, NT-S100A8 exerts a mild effect on PC cell growth, while it reduces PC cell invasion, possibly by Akt and NF-κB signaling, NT-S100A8 enhances [Ca(2+)](i) oscillations and insulin release, probably by inducing Ca(2+) influx from the extracellular space, but it does not interfere with insulin signaling.

Inflammation and pancreatic cancer: molecular and functional interactions between S100A8, S100A9, NT-S100A8 and TGFβ1

“…In a previous study we demonstrated that PDAC tissue is enriched by the biologically active N-terminal 14 aa fragment of S100A8 (NT-S100A8) [34]. In this study, in order to further exploit tumor stoma interactions, we first verified whether tumor cells release soluble mediators able to fragment the S100A8 protein.…”

“…The levels of calcium binding proteins S100A8 and S100A9 increase in cancer, including PDAC; although mainly expressed by tumor-infiltrating inflammatory cells, they may also be expressed by PDAC cells [31,34]. These proteins are directly involved in piloting metastases by the ligation of TLR4 and RAGE receptors [29,30,44].…”

“…This chromosome region [26,27] as well as S100A8/A9 TLR4 and RAGE receptors [28-30], has been associated with cancer development and metastasis. In PDAC, S100A8/A9 are overexpressed by infiltrating inflammatory cells [31,32], the levels of expression appearing to be correlated with TGFβ1 signaling: Smad4 depletion is associated with reduced S100A8 (not S100A9) positive infiltrating inflammatory cells [31,33] and, conversely, these proteins are expressed by PDAC cell lines only in cases of Smad4 inactivation [34]. The existence of an interaction between S100A8, S100A9 and the TGFβ1 canonical signaling pathway is supported by the finding that both molecules induce Smad1 and Smad2 phosphorylation through a RAGE dependent mechanism [33].…”

“…The existence of an interaction between S100A8, S100A9 and the TGFβ1 canonical signaling pathway is supported by the finding that both molecules induce Smad1 and Smad2 phosphorylation through a RAGE dependent mechanism [33]. Since S100A8 and S100A9 are calcium binding proteins, the complexity of their effects on tumor biology may depend not only on TLR4 and/or RAGE ligation, but also on alterations in intracellular calcium fluxes and/or concentrations, demonstrated to occur in pancreatic β-cells exposed to the 14 N-terminal aminoacid peptide of S100A8 (NT-S100A8), which we isolated from PDAC tissues of patients with PDAC-associated diabetes mellitus [34]. Variations in intracellular calcium, critical events that regulate cancer cell proliferation and progression, may be explained by the complex effects of calcium on different cancer cell signaling pathways, including the Ca-calmodulin protein kinase cascade, Akt, mTOR and TGFβ1 [35-40].…”

Usefulness of MALDI-TOF/MS Identification of Low-MW Fragments in Sera for the Differential Diagnosis of Pancreatic Cancer

“…4,5 Reportedly, more than 80% of patients with PaCa have frank DM or a reduced glucose tolerance, 6,7 and this frequently encountered metabolic alteration is believed to be caused by PaCaderived diabetogenic products, including the low molecular weight diabetogenic S100A8 fragment previously isolated in our laboratory. 8 These observations have prompted some investigators to suggest that patients presenting with new-onset DM should undergo screening for PaCa. 9Y11 However, the appropriate serum marker for screening in patients with diabetes has yet to be identified, since CA 19-9 is not feasible for this purpose, because it is limited in sensitivity and, in patients with diabetes, it might increase in the event of diabetic complications.…”