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Title: Involvement of Voltage-gated Na Channels in Motile Behaviour and Contractolation of Endocrine Resistant Breast Cancer Cells
Authors: فاطمة حسن محمد 
Supervisor: Prof. Yunus Luqmani
Keywords: Endocrine Resistant Breast Cancer Cells
Issue Date: 2015
Publisher:  Kuwait university - college of graduate studies
Abstract: iv ABSTRACT Voltage-gated Na+ channels (VGSCs) are membrane proteins composed of a pore-forming α subunit and an auxiliary β subunit that are normally expressed in excitable cells but have also been detected in cancer cells, where they are thought to be involved in malignancy progression. In this study we examined i), VGSC (Nav1.5) expression in breast cancer cells and its putative role in metastatic behaviour and ii), the involvement of Nav1.5 channels in pH-induced “contractolation”, in estrogen receptor (ER) silenced cells (pII). Nav1.5 was localised in cells by immunofluorescence. Its expression, as well as that of several associated signalling molecules critical for cell invasion and motility, was quantified by western blotting. Cell invasion (under-agarose assay), motility (wound healing assay) and proliferation (MTT assay) were assessed in pII cells in response to VGSC blockers, phenytoin (PHT) and tetrodotoxin (TTX), or by siRNA knockdown of Nav1.5. Total matrix metalloproteinase (MMP) was determined using an activity assay. Quantitative PCR was used to determine mRNA expression of the protein channels during contractolation. Nav1.5 showed cytoplasmic and perinuclear expression in both MCF-7 and pII cells at pH 7.4. Treatment of pII with PHT, TTX and siRNA significantly reduced invasion, in part through modulation of Akt and ERK1/2 phosphorylation and total MMP activity. The two drugs had differential effects on pII cell motility and proliferation; i.e. PHT inhibited motility while high TTX concentrations reduced cell proliferation. At alkaline pH, pII cells become spherical with actin-rich bleb-like structures on their outer membrane which contained Nav1.5. pII cells also showed enhanced expression of Nav1.5, NCX1.7, Na+/K+ ATPase and Eag 1 channel mRNAs and decreased expression of NHE-1. It is suggested that ion fluxes through these and other channels are responsible for the distinctive cell morphology and enhanced invasive potential observed during contractolation. We propose that pharmacological or genetic blockade of Nav1.5 may serve as a potential anti-metastatic therapy for breast cancer.
Appears in Programs:2050 Molecular Biology

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