Hyperglycemia-induced S100A8 and S100A9 expression target AKT, mTOR and NF-kB signalling in pancreatic cancer cells

Introduction: S100A8/S100A9 inflammatory proteins are suggested to be involved in pancreatic cancer (PaCa) progression and in cancer-associated diabetes mellitus (DM ). Aims: to analyze S100A8/S100A9 expression levels in PBMC of patients with PaCa, chronic pancreatitis (ChrPa) or pancreatobiliary tract tumors (PBT) and ascertain whether they differently affect Akt, mTOR and NF -kB signalling in PaCa cells with different aggressiveness. Methods: S100A8 and S100A9 mRNA was quantified by RT-PCR in 55 PaCa, 12 ChrPa, 15 PBT. S100A8, S100A9 and S100A8/A9 effects on Akt (Ser473,Thr308), mTOR (Ser2448) and NF -kB (p-IkB-a) were WB analyzed using BxPC3, Capan1 and MiaPaCa2. Results: S100A8 and S100A9 mRNA did not vary between groups (F=0.65, p:ns and F=2.75, p:ns), but correlated with plasma glucose (r=0.22,p=0.05; r=0.46,p<0.0001), HbA1c (r=0.11,p:ns; r=0.37,p=0.002) and insulin (0.37,p=0.008; r=0.46,p=0.001). In BxPC3 Akt was Thr308 phosphorylated by S100A8/A9, while in Capan1 and MiaPaCa2 S100A8/A9, S100A8 and S100A9 phosphorylated both Akt sites. In BxPC3 mTOR was phosphorylated (Ser2448) by S100A8. In Capan1 and MiaPaCa2 S100A8, S100A9 and S100A8/A9 caused significant Ser2448 phosphorylation. S6RP, downstream effector of mTORC1, was phosphorylated (Ser235/236) only in S100A8 treated MiaPaCa2. A strong NF -kB activation was induced by S100A8 in BxPC3, by S100A9 and S100A8/A9 in Capan1; NF -kB was inhibited by both molecules in MiaPaCa2. Conclusions: In PaCa-associated DM high expression levels of these proteins might favour cancer cell growth by inducing Akt, mTOR and NF -kB. In the less invasive BxPC3 cells S100A8 activates NF -kB. In more aggressive Capan1 and MiaPaCa2 cells S100A8, S100A9 and S100A8/A9 activate mainly Akt and mTORC1, not NF -kB pathways.