A molecular dissection of the interplay between diabetes and cancer: an integrated, multidisciplinary approach

This research combines molecular science, cell biology and disease processes - it is in molecular medicine. The research programme focuses on human insulin and Insulin-like Growth Factors I and II (IGF-I/II); these are closely related protein hormones. Their separate evolution has resulted in their acquiring separate biological functions, with insulin becoming a key regulator of metabolism, while IGF-I/II are major growth factors. When released into the blood the hormones bind, tightly and specifically, to their receptors, (Insulin Receptor (IR) and IGF-1R respectively); these are large complex protein molecules on the cell surface. Receptor binding, through which the hormone activity is expressed, involves structural changes in both the hormone and the receptors.

Despite their fundamental medical importance (insulin: in diabetes, IGFs: in development, cancer, aging) the active conformations of the hormones in their hormone:receptor complexes are not known. Thus, more than 40 years after the first insulin crystal structure was determined, all the analogues used in treatment of diabetes are still based on the inactive/storage forms of this hormone.

Insulin cross-reation with IGF-1R and its accumulation in Type 2 Diabetes entails this hormone in cell proliferation and growth. As IGF-I/II are also cancer-specific growth factors the identification of pure 'metabolic' and 'cell growth' structural signatures of insulin and IGF-I/II is of fundamental importance not only for the understanding of the biology of these hormones, but also for new, effective treatments of diabetes and cancer. Therefore this Programme is a response to an urgent need for a unique, consolidated, and multidisciplinary attack on these critical problems of insulin and IGF-I/II structure and biology.

This programme combines fundamental (structural biology, cell signaling, organic and protein chemistry) and applied research. The fundamental research provides the foundations of the programme. However, advanced expertise of this group in the applied biomedical sciences will enable parallel pursuit of applied aims as well.
This programme will deliver: (i) 3-D structural description of insulin:IR complexes; elucidation of the active form of human insulin, (ii) identification of active surfaces in insulin's responsible for metabolic effects, (iii) development of novel, specific metabolic insulin analogues, (iv) identification of the mitogenic structural signatures of the Insulin-like Growth Factors-I/II (IGF-I/II) expressed through IR, (vi) initiation of developing organo/peptido-mimetics of these hormones.

We believe that the potential impacts on molecular cell biology and on medical science are immense as it addresses directly two major health problems, diabetes and cancer. Both have enormous social and economic consequences. (i) Firstly, solution of the central problem of diabetes: insulin-Insulin Receptor (IR) interaction, i.e. activation of insulin from its storage form to its IR stimulating conformation, will provide a long-awaited breakthrough in understanding of insulin structure-function relationships and open new possibilities for rational design of novel insulins. (ii) Subsequently, identification of structural determinants of insulin and IGF-I/II that govern their specific signaling pathways and which are responsible for metabolic and growth specificity of these hormones should enhance the prospects for rational design and production of pure and safe insulins without their undesired mitogenic properties. This is a problem indicated by some currently used clinical analogues. (iii) The studies should allow initiation of rational design and synthesis of IGF-I/II-specific antagonists for novel anti-cancer therapies. (iv) The firm control on hormone chemistry within this programme will also allow initiation of rational design and synthesis of organo-mimics of insulin, which may lead to insulin-like drugs suitable for oral delivery.

The major experimental goals are the production of the IR construct (in a large-scale mammalian cell expression facility) and its crystallization with selected high affinity analogues. This will be followed by their X-ray crystallographic analysis. This research in turn, rests on chemical semi- and full-synthesis of insulin and IGF analogues and their structural and biological characterization, especially their binding affinity.

Crystals of IR constructs, one complexed with insulin and another with a high affinity analogue, have already been prepared. The immediate goal is now to improve the diffracting power of these crystals (currently at ~ 4.5 - 3.9 Å). The range of insulin analogues will be exploited and alternative receptors investigated if necessary. X-ray data collection will be undertaken at synchrotrons.
The structural changes in insulin and the receptor associated with complex formation will be analysed and compared to the native hormone's solution structure. With this information another cycle of insulin analogue synthesis and analysis will be undertaken. Experiments will be carried out to explore the functional roles of residues on insulin's receptor-binding surface. This work will be paralleled by synthesis of new insulins with novel chemistry. Insulin and IGF-I/II hybrids will also be synthetised and their structures (alone and in complex with IR) determined to give insight into the structural basis of the different specificity of these homones. Cell signalling profiles of all analogues will be monitored.

The programme involves four centres: University of York (YSBL) - structural biology, Institute of Organic Chemistry and Biochemistry (IOCB, Prague) - chemical biology, organic and protein chemistry, insulin affinity/potency essays, drug design/synthesis, University College Cork (UCC) - cell biology/signalling, Walter and Eliza Hall Institute of Medical Research, Melbourne (WEHI) - molecular and structural biology of IR.

The research on insulin and its receptor proposed in this Programme will have a fundamental impact on understanding insulin's mechanism of action - and that of other related hormones/factors. Despite 40 years of intensive structural studies we still do not know the structure of the active form of insulin although we know that it must be different from its well-characterized storage and solution forms. Nor is an accurate structure of the insulin:Insulin Receptor complex known. With insight into insulin's structure and its contacts in its receptor- bound/active conformation, the nature of the hormone fold, the invariance of its amino acids distribution will be understood properly - at last. Most importantly, the design of new insulin analogues with new structures and properties will be possible.

Insulin and the closely related hormones IGF-I and IGF-II interact with each others receptors, this implies that insulin is not only involved in metabolic regulation but also in cell proliferation and growth. The active forms of IGF-I and II are also unknown. Progress in novel clinical approaches to diabetes and cancer is hindered by ignorance of the specific structural signatures in insulin and IGF-I/II responsible for their different metabolic and growth signaling properties. The proposed research programme is directly relevant to two major human diseases: diabetes and cancer, both of which present huge social and economic burdens. The "epidemic"-like scale of diabetes in particular presents an urgent and a long-term problem.
The importance of this research, and its urgency, is highlighted by the increase in certain forms of cancer (e.g. colorectal, breast) in Type 2 Diabetes, and a >50% increase in cardiovascular disease, stroke and kidney disease, and long-term complications directly linked to diabetes.

The main Programme's impact will come from:

(i) Understanding the structures involved in insulin-Insulin Receptor (IR) interaction, i.e. the activation of insulin from its storage/solution form to its IR stimulating conformation, will be described for the first time in 3-D detail. This will provide a breakthrough in understanding insulin structure-function relationships and open new possibilities for rational design of novel insulins by non-commercial and Pharmaceutical laboratories.

(ii) Subsequently, structures of more novel insulin analogues and their hybrids with IGF-I/II (both free and in complexes with IR) will be determined and their functions/functional effects will be characterized. This molecular approach should enable identification of structural determinants of insulin and IGF-I/II that govern their specific signaling pathways and which are responsible for the metabolic and growth specificity exhibited by these modified hormones. The results will extend the models available for more rational design and for production of safe insulins with only specific metabolic functions; we expect strong interest from the pharmaceutical industry in exploiting these discoveries.

(iii) The new structural information on the 'active' structures will also guide rational design and synthesis of insulin organo-mimics in this programme that may lead to new approaches in development of insulin-like drugs suitable for oral delivery. We anticipate that the new basis for rational drug design provided by the structures of the hormones/analogues in their receptor complexes will stimulate pharmaceutical research and development of oral treatments for diabetes and cancer.