Title: The Insulin-like Growth Factor 2/ Mannose 6-phosphate receptor and tumour growth control
Funder: Cancer Research UK

Abstract: The purpose is to treat tumours by reducing the supply of the potent embryonic and tumour growth factor, Insulin-like growth factor 2 (IGF2), with soluble forms of the IGF2/ Mannose 6-phosphate receptor (IGF2/M6PR). 1. Background: Increased free IGF2 secondary to the combined loss of clearance function of IGF2/M6PR, M6P-lysosomal protease cleavage of IGF binding proteins, and increased IGF2 expression via loss of imprinting, can lead to embryonic overgrowth and cancer promotion by IGF1 receptor (IGF1R) signaling pathway activation. Circumstantial evidence suggests that reducing IGF2 supply might limit tumour growth, although direct evidence is absent in humans because of the lack of an IGF2 antagonist. 2. Relevance: IGF2 supply is an important treatment target as it is increased in hepatocellular, sarcoma, colorectal, ovarian, breast, and childhood cancers. Pathway activation is entirely dependent on ligand supply as IGF1R is rarely mutated, and receptors IGF1R and IR (Isoform A) are preformed. IGF1R kinase inhibitors and monoclonal antibodies predominate as therapeutic strategies, with significant activity in EWS-FLI sarcoma and in common cancers in combination with chemotherapy. Specific targeting of bio-available lGF2 in tumours circumvents the systemic effects of IGF1R inhibition, feedback up-regulation of IGF1, and cross reaction with IR(A). 3. The proposal aims to: -Exploit the structure of IGF2/M6PR to generate high affinity soluble receptor (domain 11) that targets IGF2 for degradation (collaboration). -Test the hypothesis that IGF2 supply is required for the maintenance of tumour growth. -Test the hypothesis that lysosomal protease bioavailability regulated by M6P binding also controls IGF2 supply. - Determine the structural basis of the specificity of domain 9 for M6P. - Exploit domain 9 to generate a high affinity soluble receptor that targets M6P lysosomal proteases for inhibition. 4. The research plan will: - Determine high resolution structure of IGF2 bound to domain 11 by NMR. -Evaluate the structure and function of N-terminal tagged IGF2 prior to a knock-in murine model. -Evaluate conditional (Cre/loxp) expression of Igf2 and Igf2r combined with conditional loss of Apc, Cdh1, p53 and Pten induced tumours. - Optimise domain 11-Fc fusion protein avidity using Pichia pastoris directed evolution and selection. - Generate xenograft models of IGF2 dependent tumour progression and regression for therapeutic testing (with Cancer Research Technology). - 18F-label optimised domain11-Fc for murine targeting studies (with Chemistry, Oxford). - Determine high resolution structure of M6P bound to domain 9 and derive high affinity mutants (NMR and X-ray crystallography). -Generate and test effects of chimeric domain 9 on the catalytic function of lysosomal proteases. - Evaluate the growth and tumour effects of conditional knock-in inactivating mutations of Igf2r domains 3+9 and domain 11, and the G1619R human polymorphism. - Evaluate genetic complementation of conditional knockout of IGF2/M6PR in cells.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS;5.2 CELLULAR AND GENE THERAPIES
Health categories: CANCER AND NEOPLASMS