Glucagon acts through binding to its receptor, glucagon receptor (GCGR), and cross-talk between GCGR-mediated signals and signaling pathways that regulate cancer cell fate has been unveiled.
The data suggest that GLP-2 stimulates cancer myofibroblast proliferation, migration and invasion; GLP-2 acts indirectly on epithelial cells partly via increased IGF expression in myofibroblasts and partly, perhaps, by increased bioavailability through degradation of IGFBPs.
It has been reported that glucagon-like peptide-1 (GLP-1) agents have been associated with both the increased risk of cancer and inhibition of tumor growth and metastases.
Since CXCL5 expression is increased in patients with type 2 diabetes, and GLP-2, CXCL5 and SDF-1 are associated with tumor progression, DPP-4 inhibition may have potential as an agent for decreasing the risk of cancer in obese or diabetic patients.
After treatment of the three cancer cell lines with different doses of the (pro)enzymes for up to 7 days, we observed (i) growth inhibition in a dose-dependent manner, (ii) enhanced expression of β-catenin and E-cadherin and decreased expression of several epithelial-mesenchymal transition (EMT)-associated genes, such as Vimentin, Snail and Slug, (iii) differentiation of Caco-2 cells, including the appearance of cell-specific differentiated structures such as microvilli and tight junctions, the acquisition of a more regular polygonal morphology, and an increased expression of the intestinal differentiation markers alkaline phosphatase and cytokeratin 8, and (iv) differentiation of Panc1 cells, including the formation of cell aggregates, an increment on lamellar bodies and an increased expression of the pancreatic differentiation markers glucagon and insulin.
Haplotype analysis showed that in comparison with the most common haplotype (A(1)GCG), the A(2)CCG haplotype was associated with an increased risk (OR 1.39; 95% CI 1.02-1.88; P = 0.034) and the A(1)CCG with a reduced risk (OR 0.30; 95% CI 0.12-0.76; P = 0.011) for this cancer.
The pancreatic tissue from the four patients contained more than 870 microadenomas and 10 macrotumors, all of which expressed exclusively glucagon and none of which showed evidence of malignancy.