Role of insulin receptor isoform A in breast cancer
Date
2017
Authors
Li, Liang
Editors
Advisors
Forbes, Briony Evelyn
Hoffmann, Peter
Hoffmann, Peter
Journal Title
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Type:
Theses
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Abstract
Insulin like growth factor II (IGF-II) binds to Insulin Receptor isoform A (IR-A) to sustain
cell growth and proliferation. This autocrine loop exists in many human carcinomas and
provides an additional proliferation and survival pathway to the type 1 insulin-like growth
factor (IGF-1R) signalling pathway. In addition, activation of the IGF-II/IR-A autocrine loop
provides a mechanism of resistance drugs target the type 1 insulin-like growth factor (IGF-
1R). However, the mechanism of how IGF-II/IR-A differentiates itself from the IGF-II/IGF-
1R pathway is still unclear. Additionally, a novel phosphorylation site Thr¹¹⁴⁸ (numbered in
IR-A) of IR was found in response to insulin stimulation and its phosphorylation in the
absence of any Tyr¹¹⁴⁶, Tyr¹¹⁵⁰, and Tyr¹¹⁵¹ phosphorylation. We thus hypothesis that the The phosphorylation of Thr¹¹⁴⁸ inhibits the phosphorylation of Tyr¹¹⁴⁶, Tyr¹¹⁵⁰, and Tyr¹¹⁵¹ of the
activation loop, which is possibly due to steric hindrance and electrostatic repulsion of the
phosphate group on Thr¹¹⁴⁸ preventing interaction of the activation loop with the tyrosine
kinase.
The key areas of investigation included:
1. Investigate the role of Thr¹¹⁴⁸ phosphorylation in IR-A by overexpress the wild-type
IR-A and its mutants Thr¹¹⁴⁸Ala and Thr¹¹⁴⁸Asp in R⁻ (Mouse fibroblast cells with IGF-
1R KO).
2. Knock down the IR and IGF-1R separately in MDA-MB-231 and MCF-7 cells using
inducible expressed miR30 shRNA and measure their characteristics (proliferation,
migration, epithelial–mesenchymal transition) in response to insulin, IGF-I, and IGFII
stimulation separately.
3. Quantitative phosphoproteomics was conducted to compare the insulin/IR-A and IGFII/
IR-A signalling pathway with MDA MB 231 IGF-1RKD cell.
The key findings from this work included:
included:
1. Thr¹¹⁴⁸Ala and Thr¹¹⁴⁸Asp inhibit the insulin sensitivity of IR-A, which indicate the
Thr¹¹⁴⁸ phosphorylation inhibits the IR activation.
2. IRKD has no effect on proliferation of MCF-7 cells and the migration of MDA-MB- 231 cells, but increases the proliferation of MDA-MB-231 cells.
3. IGF-1RKD inhibits the proliferation of both MCF-7 cells and MDA-MB-231 cells,
but increases the migration of MDA-MB-231 cells.
4. IGF-1R increases the insulin sensitivity of MDA-MB-231 cells, shown by the Akt
activation.
5. Insulin and IGF-II are confirmed to induce different signalling pathways confirmed by
quantitative phosphoproteomics study. IGF-II is preferentially regulates the migration
and stemness of MDA-MB-231 IGF-1RKD cells. Many markers are identified but
verifications are still needed. Drug developed on the verified markers can be used to
treat the patients who are resistant to anti-IGF-1R inhibitor.
School/Discipline
School of Biological Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2018
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