Role of insulin-like growth factor-type 1 receptor (IGF-IR) signalling in tamoxifen-resistant breast cancer

Knowlden, Janice M. 2008. Role of insulin-like growth factor-type 1 receptor (IGF-IR) signalling in tamoxifen-resistant breast cancer. PhD Thesis, Cardiff University.

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Abstract

The aim of the first part of this thesis was to determine the role played by IGF-IR in mediating the growth of EGFR-positive tamoxifen-resistant variants of MCF-7 Tam-R and T47D T47D-R breast cancer cell lines. The results identify a general tamoxifen-resistant mechanism whereby the autocrine release and action of IGF-II, mediated through the IGF-IR, plays a significant and crucial supporting role in regulating basal EGFR/MAPK signalling and cell proliferation and this occurs via a c-SRC-dependent mechanism in both Tam-R and T47D-R cells. The latter aim of this thesis was to determine further mechanisms of cross-talk between EGFR and IGF-IR in a range of EGFR-positive cancer cell lines. These studies identified a novel physical interaction between the EGFR and IRS-1 in each of these cell lines. In Tam-R breast and LNCaP prostate cancer cells, recruitment of IRS-1 by EGFR limited the availability of IRS-1 to associate with IGF-IR, thus inhibiting IGF-IR signalling capacity. Blockade of EGFR activity with gefitinib allowed re-association of IRS-1 with IGF-IR and re-establishment of IGF-IR signalling, the dominant growth regulatory mechanism of gefitinib resistance in Tam-R cells. Thus, gefitinib played an active role in limiting its own efficacy in these cells by promoting activation of a resistance pathway. Importantly, induction of this pathway by gefitinib could be abrogated by co-treatment with an IGF-IR inhibitor. Such findings identify the IGF-IR as a potential therapeutic target for the treatment of both tamoxifen-resistant and gefitinib-resistant breast and prostate cancers.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Schools > Pharmacy
Subjects:	R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology (including Cancer) R Medicine > RM Therapeutics. Pharmacology
ISBN:	9781303182242
Funders:	Tenovus
Date of First Compliant Deposit:	30 March 2016
Last Modified:	16 Apr 2025 15:31
URI:	https://orca.cardiff.ac.uk/id/eprint/55695

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