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Title: Collateral resistance to oestrogen and erbB receptor activated growth in endocrine resistant breast cancer
Author: Moore, Kate
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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A panel of breast cancer cell lines (MIII, LCC1, LCC2, LCC9, LY2) derived from the MCF-7 breast cancer cell line with varying oestrogen and anti-oestrogen insensitivity (termed ‘resistant’) was used as a model to determine signalling pathways which may contribute to the development of this insensitivity. 17β-oestradiol (E2) only significantly stimulated growth in MCF-7, MIII and LCC1 cell lines. Resistant cells were insensitive to growth factors, while MCF-7 cells remained responsive. MIII and LCC1 cells retained some tamoxifen sensitivity, while the remaining cell lines were unaffected. ERα expression was determined and ‘cross-talk’ was investigated by monitoring ERα activation via phosphorylation of serine residues 118 and 167 (P-S118/167) using western blotting. MIII, LCC1 and LCC2 cell lines expressed more ERα than MCF-7 cells, which may account for elevated basal growth in these lines. The remaining cell lines expressed similar ERα levels to MCF-y cells, hence another mechanism must account for elevated basal growth in these cells. ERα was subject to E2 ‘turnover’ in all cells, indicating all cells contain functional ERα. ERα activation was then elucidated by observing P-S-118 and P-S167. Of interest, E2 significantly enhanced P-S118 in LCC1 cells to a greater extent than MCF-7cells. Little or no P-S117 was observed in LCC9 cells irrespective of treatment. LCC1 and LCC9 cell lines were further investigate in comparison to MCF-7 cells as they displayed a progressive loss of E2 and anti-E2­ ­sensitivity. No differences in P-S167 expression were observed between cell lines subject to control or E2 treatment; HRGβ enhanced P-S167 to an equal extent in all cells. To investigate which upstream molecules may account for the changes in P-S118, the expression and activation of Akt, MEK and ERK were determined. Total levels of all three proteins were equivalent in all cells. Akt was significantly constitutively phosphorylated in the resistant cell lines compared to MCF-7 cells, suggesting this pathway is important in the development of resistance. TGFα and HRGβ significantly enhanced P-Akt in al three cell lines to a similar extent. HRGβ enhanced P-MEK in MCF-7, LCC1 and LCC9 cell lines, but this diminished as resistance progressed, suggesting a reduction in the involvement of this pathway. However, expression of P-ERK, which is downstream of MEK, was equivalent across all three cell lines, indicating that P-ERK was not responsible for endocrine resistance in this model. The novel recombinant humanised anti-erbB2 monoclonal antibody 2C4 (2C4) inhibited growth factor enhanced proliferation in MCF-7 cells via diminished P-Akt and PERKI/II activation. 2C4 significantly reduced HRGβ-enhanced P-Akt and P-ERKI/II in the resistant cell lines indicating these pathways may be partially responsible for some growth of these cells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available