Activation of insulin receptors and IGF-1 receptors in COLO-205 colon cancer xenografts by insulin and insulin analogue X10 does not enhance growth under normo- or hypoglycaemic conditions
Recent studies with normal rats and mouse allograft models have reported that insulin and insulin analogues do not activate the IGF-1 receptor in vivo, and that this characteristic therefore cannot be responsible for the increased incidence of mammary tumours observed for the insulin analogue X10 in chronic toxicity studies with Sprague Dawley rats. This is in clear contrast to reports of insulin and insulin analogues in vitro. Clarification of this is important for understanding the mechanisms behind possible growth-promoting effects of insulin analogues, and will have implications for the development of novel insulin analogues.
We established a xenograft model in BALB/c nude mice with the human colon cancer cell line COLO-205, which expresses human insulin and IGF-1 receptors, and explored the acute and chronic effects of treatment with supra-pharmacological doses of human insulin, insulin analogue X10 and human IGF-1. With a novel antibody, acute IGF-1 receptor activation was also examined in various tissues from normal rats treated with human insulin, insulin analogue X10 or human IGF-1. Finally, the effects of pharmacologically relevant doses of human insulin and insulin analogue X10 on receptor activation and growth of COLO-205 xenograft were explored in BALB/c nude mice with alloxan-induced hyperglycaemia.
In normal rats and in BALB/c nude mice bearing a COLO-205 cell xenograft, treatment with supra-pharmacological doses of human insulin, insulin analogue X10 or human IGF-1 resulted in activation of insulin receptors as well as IGF-1 receptors. Treatment of diabetic nude mice with pharmacologically relevant doses of human insulin or insulin analogue X10, which decreased blood glucose from hyperglycaemic levels to the normoglycaemic range, did not increase IGF-1 receptor activation. Furthermore, repeated treatment with supra-pharmacological as well as pharmacological doses of human insulin or insulin analogue X10 did not influence the growth of COLO-205 xenografts.
This study demonstrates that activation of IGF-1 receptors in cancer cells by insulin and insulin analogues cannot be considered as a purely in vitro phenomenon. It does occur in vivo in animal models, although only after treatment with supra-pharmacological doses. Furthermore, treatment with insulin or insulin analogue X10 did not influence the growth of COLO-205 xenografts under normo- or hypoglycaemic conditions. Further studies are needed before a conclusion can be reached on whether IGF-1 receptor activation by insulin analogues correlates with increased growth in vivo.
KeywordsIGF-1 IGF-1 receptor activation Insulin Insulin analogues Insulin receptor activation
We thank A. Bowman, S. L. Riisberg and K. S. Tornqvist for technical assistance with the animal experiments, and P. Jensen, M. Stendal and C. H. Dahl for performing ELISAs for insulin receptor, IGF-1R and Akt activation (all at Insulin Research, Novo Nordisk, Maaloev, Denmark).
This study was conceived and designed by HH, MSJ, NB, RS, AL, BFH. Acquisition of data was performed by HH, MSJ, NB, AL and BFH. Data were analysed and interpreted by HH, MSJ, NB, RS, AL and BFH. The manuscript was drafted and revised by HH, MSJ, NB, RS, AL and BFH. All authors gave final approval of the version to be published. HH is the guarantor of this work.
This study was funded entirely by Novo Nordisk. Representatives from Novo Nordisk other than the authors provided editorial assistance only.
Duality of interest
All authors are employees at Novo Nordisk and own shares in the company.
- 17.Committee for the Update of the Guide for the Care and Use of Laboratory Animals (2011) Guide for the Care and Use of Laboratory Animals. The National Academies Press, Washington DCGoogle Scholar