Conclusions/interpretation
Our results suggest that all tested insulin compounds may stimulate tumour growth by enhancing local angiogenesis. Future studies need to confirm the association between insulin therapy in type 2 diabetes and tumour progression.
Methods
Five types of human adenocarcinoma (breast, colon, pancreas, lung and kidney) were evaluated for the presence of insulin receptors (IRs) on angiogenic structures. In an in vitro angiogenesis assay, various commercially available insulin compounds were evaluated for their potential to increase capillary-like tube formation of human microvascular endothelial cells (hMVEC). Insulin compounds used were: human insulin, insulin lispro (B28Lys,B29Pro human insulin), insulin glargine and insulin detemir (B29Lys[e-tetradecanoyl],desB30 human insulin).
Results
Insulin receptors were found to be strongly expressed on the endothelium of microvessels in all evaluated adenocarcinomas, in addition to variable expression on tumour cells. Low or no detectable expression of IRs was seen on microvessels in extratumoral stroma. Incubation with commercially available insulin compounds increased capillary-like tube formation of hMVEC in vitro. Conclusions/interpretation: Our results suggest that all tested insulin compounds may stimulate tumour growth by enhancing local angiogenesis. Future studies need to confirm the association between insulin therapy in type 2 diabetes and tumour progression.