Surface‐expressed insulin receptors as well as IGF‐I receptors both contribute to the mitogenic effects of human insulin and its analogues

Abstract

There is a medical need for new insulin analogues. Yet, molecular alterations to the insulin molecule can theoretically result in analogues with carcinogenic effects. Preclinical carcinogenicity risk assessment for insulin analogues rests to a large extent on mitogenicity assays in cell lines. We therefore optimized mitogenicity assay conditions for a panel of five cell lines. All cell lines expressed insulin receptors (IR), IGF-I receptors (IGF-IR) and hybrid receptors, and in all cell lines, insulin as well as the comparator compounds X10 and IGF-I caused phosphorylation of the IR as well as IGF-IR. Insulin exhibited mitogenicity EC(50) values in the single-digit nanomolar to picomolar range. We observed correlations across cell types between (i) mitogenic potency of insulin and IGF-IR/IR ratio, (ii) Akt phosphorylation and mitogenic potency and (iii) Akt phosphorylation and IR phosphorylation. Using siRNA-mediated knockdown of IR and IGF-IR, we observed that in HCT 116 cells the IR appeared dominant in driving the mitogenic response to insulin, whereas in MCF7 cells the IGF-IR appeared dominant in driving the mitogenic response to insulin. Together, our results show that the IR as well as IGF-IR may contribute to the mitogenic potency of insulin. While insulin was a more potent mitogen than IGF-I in cells expressing more IR than IGF-IR, the hyper-mitogenic insulin analogue X10 was a more potent mitogen than insulin across all cell types, supporting that the hyper-mitogenic effect of X10 involves the IR as well as the IGF-IR. These results are relevant for preclinical safety assessment of developmental insulin analogues.

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

“…1). This is in good agreement with previous findings that COLO-205 cells express six-to sevenfold higher levels of IGF-1R than insulin receptor (predominantly isoform A of insulin receptor) [16,20].…”

“…The mitogenic potencies of human insulin, X10 and IGF-1 were assessed in COLO-205 cells (ATCC, Manassas, VA, USA) as described previously [16]. COLO-205 cells for injection in mice were trypsinised, washed once in PBS, re-suspended in PBS at a concentration of 10.0 × 10 6 cells/ml and kept on wet ice until injection.…”

Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

“…The MAPK pathway is one of the major signaling routes induced by IR autophosphorylation and is responsible for cell proliferation ( 21 , 22 ). Of particular importance is the effect of insulin on cell proliferation in some cancer cell lines ( 23 , 24 ). Because IR-A48 did not activate the MAPK pathway (Figure 4A and D ), we investigated whether IR-A48 has an effect on cell proliferation.…”

“…To date, a variety of insulin analogs that have modified amino acid sequences have been successfully used in diabetes patients for normal glycemic control. However, insulin treatment is also considered to promote cell proliferation and the amino acid modifications of some insulin analogs increase their binding affinity and activation of IGF1-R ( 23 , 35 , 36 ). Accordingly, long-term use of insulin analogs for diabetes care has raised concerns regarding increased cancer risk ( 37 ) and several epidemiological reports showed correlations between prolonged insulin treatment and increased cancer risk ( 38 – 42 ).…”

Targeting Insulin Receptor with a Novel Internalizing Aptamer

“… 11 , 12 , 13 , 14 Activation of both receptors plays a key role in normal tissues physiology and has been implicated in cancer development and progression. 15 , 16 While different inhibiting strategies for IGF-1R have already been developed as anticancer therapeutics (including monoclonal antibodies and small molecules), 17 the importance of IR pathway in cancer development has been addressed more recently.…”