Identifying new approaches to the treatment of endocrine resistant breast cancer
File(s)
Author(s)
Balachandran, Kirsty Anushka
Type
Thesis
Abstract
Estrogen receptor α (ER) plays a key role in the development and progression of breast cancer and is targeted by endocrine therapies used to treat this disease. However, resistance to these therapies remains a major therapeutic challenge. Estrogen receptor gene (ESR1) mutations have been implicated as a mechanism of resistance in 20-30% of metastatic, ER-positive breast cancers. The gene-editing system, CRISPR-Cas9, has previously been used to model these mutations in MCF7 cells in my host laboratory. The MCF7-Y537S cell line, with substitution of tyrosine for serine at position 537, has been shown to exhibit estrogen-independent growth, partial resistance to anti-estrogens and upregulation of many ERα target genes, including the progesterone receptor gene (PGR). Several reports have demonstrated that, on ligand-activation, the progesterone receptor (PR) reprogrammes the genomic binding pattern and transcriptome of ER into a less tumorigenic profile. Hence PR ligands may have utility in ESR1 mutant breast cancer. A T47D-Y537S cell line has also previously been created in the laboratory in the same way as MCF7-Y537S cells, using CRISPR-Cas9. Here, I have characterised the T47D-Y537S cell line to check the presence of the Y537S mutation, confirm its ligand-independence and, furthermore, determine its utility for studying PR activity in this setting. I demonstrate that some PR agonists, but not PR antagonists or siRNA-mediated PR knockdown, inhibit the growth of T47D-Y537S cells. To elucidate the role of PR signalling in breast cancer with wildtype (WT) and Y537S ER, I define a set of PR-regulated genes in T47D-WT and T47D-Y537S cells, using RNA-seq. I also identify an anti-migratory effect of a PR agonist on T47D-WT and T47D-Y537S cells, through scratch wound assays and enrichment of Gene Ontology Biological Process pathways related to motility, which may have implications for the prevention of metastases in endocrine resistant breast cancer.
Version
Open Access
Date Issued
2022-08-11
Date Awarded
01/02/2023
License URL
Advisor
Ali, Simak
Buluwela, Laki
Coombes, R Charles
Sponsor
Medical Research Council (Great Britain)
Imperial College Healthcare NHS Trust
Grant Number
MR/P018521/1
Publisher Department
Department of Surgery & Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)