Invadopodia Formation in Breast Cancer

Cancer progression can be driven by signalling via growth factors such as hepatocyte growth factor (HGF) and by the surrounding microenvironment. During initial tumour expansion intratumoral hypoxia can develop due to inadequate vasculature supply. To resist the negative effect of hypoxia, cells increase expression of transcription factor hypoxia-inducible-factor-1 (HIF-1α). However, little is known about how HIF-1α might influence the invasive behaviour of the cancer cells. Cell invasion requires actin cytoskeletal reorganisation and cells are thought to utilise specialised membrane protrusions termed invadopodia. Rho family GTPases Rac and Cdc42 through interaction with effector proteins p21-activated kinases (PAKs) are known to regulate actin cytoskeletal dynamics. Indeed, PAK1/2 are over-expressed in breast cancer however the role of PAK1/2 in invadopodia formation has not been fully investigated.<br/><br/>This project sought to investigate the relationship between growth factor signalling, induction of HIF-1α expression and PAK activity during invadopodia formation in MDA-MB-231 cells. Analysis revealed that increased invadopodia formation can be induced by HGF. Furthermore, increasing levels of HIF-1α using dimethyloxaloylglicine (DMOG) treatment or overexpression of GFP-HIF-1α correlated with increased invadopodia activity that was dependent upon the expression of HIF-1α. Subsequent studies revealed that PAK1 and 2 are required for both HGF and DMOG induced invadopodia formation. However, whilst PAK1/2 were activated downstream of HGF, there was no change in PAK1/2 expression levels or activity following DMOG treatment. Interestingly both DMOG treatment and HIF-1α overexpression did lead to up-regulation of cytoskeletal protein expression including β-PIX. β-PIX interacts with PAK1 but has not been previously linked to invadopodia formation. It is shown here for the first time that a reduction in treatment. Overall, these studies demonstrate the dynamite the dynamic nature of ivadopodia formation; identity novel regulators of invadopodia activity and highlight the direct role of hypoxia in cell invasion.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2012

Author dc:creator

• Md Hashim, Fariesha

Advisors dc:contributor.advisor

• Morris, Jonathan David Hamilton
• Wells, Claire Marie

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/faf29295-e355-43a8-945b-9d17a3992ed6

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/faf29295-e355-43a8-945b-9d17a3992ed6