Breast Cancer Associated gene 2 (BCA2), is a little-studied E3 ligase that is overexpressed in 56% of all primary breast cancers and has been linked with increased cell proliferation and invasion in vitro. BCA2 has been implicated in EGFR degradation however there is conflicting evidence surrounding its function and effect on receptor biology. This project aimed to elucidate the role of BCA2 in EGFR endocytosis and downregulation and to determine its link with breast cancer survival. Data generated with online mRNA analysis tools indicated that high BCA2 levels were often associated with improved breast cancer prognosis. In silico studies also demonstrated that many genes coexpressed with BCA2 were regulators of membrane trafficking and suggested that BCA2 expression was repressed by HER2/EGFR/Ras signalling. Experimentally, it was shown that siRNA depletion of BCA2 led to increased EGFR protein levels while transient BCA2 overexpression reduced levels of the receptor. It was found that BCA2 overexpressing, EGF stimulated cells demonstrated reduced lysosomal degradation of both receptor and ligand. Associated with this, downstream EGFR signalling in BCA2 overexpressing cells was reduced in magnitude but prolonged in duration and ultimately cell viability was impaired. 3 These findings support a role for BCA2 in the endolysosomal system. In agreement with this it was shown that BCA2 overexpression inhibited the vesicle membrane association of Rab7, a regulator of late endocytosis and reported BCA2 interactor. Transferrin receptor levels and transferrin uptake were unaffected by BCA2 overexpression suggesting trafficking effects may be restricted to EGFR, a distinct class of receptor and/or to later (degradation) stages of endocytosis. This thesis provides a detailed exploration of BCA2 biology and presents evidence of a functional role for the protein in the endocytic regulation of EGFR. The mechanism/s underlying the complex relationship between BCA2 and breast cancer outcome have yet to be fully determined.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:646290 |
| Date | January 2014 |
| Creators | Wymant, Jennifer |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/72275/ |
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