BackgroundEpidemiological studies have shown direct associations between type 2 diabetes and obesity, both conditions associated with hyperglycaemia and hyperinsulinemia, and the risk of pancreatic cancer. Up to 80% of pancreatic cancer patients present with either new-onset type 2 diabetes or impaired glucose tolerance at the time of diagnosis. Recent population studies indicate that the incidence of pancreatic cancer is reduced among diabetics taking metformin. In this study, the effects of exposure of pancreatic cancer cells to high glucose levels on their growth and response to metformin were investigated.MethodsThe human pancreatic cancer cell lines AsPC-1, BxPC-3, PANC-1 and MIAPaCa-2 were grown in normal (5 mM) or high (25 mM) glucose conditions, with or without metformin. The influence by metformin on proliferation, apoptosis and the AMPK and IGF-IR signalling pathways were evaluated in vitro.ResultsMetformin significantly reduced the proliferation of pancreatic cancer cells under normal glucose conditions. Hyperglycaemia however, protected against the metformin-induced growth inhibition. The anti-proliferative actions of metformin were associated with an activation of AMP-activated protein kinase AMPKThr172 together with an inhibition of the insulin/insulin-like growth factor-I (IGF-I) receptor activation and downstream signalling mediators IRS-1 and phosphorylated Akt. Furthermore, exposure to metformin during normal glucose conditions led to increased apoptosis as measured by poly(ADP-ribose) polymerase (PARP) cleavage. In contrast, exposure to high glucose levels promoted a more robust IGF-I response and Akt activation which correlated to stimulated AMPKSer485 phosphorylation and impaired AMPKThr172 phosphorylation, resulting in reduced anti-proliferative and apoptotic effects by metformin.ConclusionOur results indicate that metformin has direct anti-tumour activities in pancreatic cancer cells involving AMPKThr172 activation and suppression of the insulin/IGF signalling pathways. However, hyperglycaemic conditions enhance the insulin/IGF-I responses resulting in an altered AMPK activation profile and prevent metformin from fully switching off the growth promoting signals in pancreatic cancer cells.

Tumour-educated macrophages display a mixed polarisation and enhance pancreatic cancer cell invasion.Karnevi, Emelie; Andersson, Roland; Rosendahl, Ann Link to publication Citation for published version (APA): Karnevi, E., Andersson, R., & Rosendahl, A. (2014). Tumour-educated macrophages display a mixed polarisation and enhance pancreatic cancer cell invasion. Immunology and Cell Biology, 92(6), 543-552. DOI: 10.1038/icb.2014.22 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal High glucose conditions further enhanced the tumour-driven macrophage enrichment and associated IL-6 and IL-8 cytokine levels. In addition, hyperglycaemia enhanced the responsiveness of tumour-educated macrophages to lipopolysaccharide, with elevated cytokine secretion compared to normal glucose levels. Tumour-educated macrophages were found to promote pancreatic cancer cell invasion in vitro, which was significantly enhanced at high glucose. The anti-diabetic drug metformin shifted the macrophage phenotype polarization and reduced the tumour cell invasion at normal, but not high, glucose levels. In conclusion, this study demonstrates that pancreatic cancer cells stimulate differentiation of macrophages with pro-tumour properties that are further enhanced by hyperglycaemia. These findings highlight important crosstalk between tumour cells and TAMs in the local tumour microenvironment that may contribute to disease progression in pancreatic cancer patients with hyperglycaemia and T2D.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractPancreatic cancer is associated with a highly abundant stroma and low-grade inflammation. In the local tumour microenvironment, elevated glucose levels, the presence of tumour-