The neonatal splice variant of Nav1.5 potentiates in vitro invasive behaviour of MDA-MB-231 human breast cancer cells

Upregulation of functional voltage-gated Na+ channels (VGSCs) occurs in metastatic human breast cancer (BCa) in vitro and in vivo. The present study aimed to ascertain the specific involvement of the "neonatal" splice variant of Nav1.5 (nNav1.5), thought to be predominant, in the VGSC-depe...

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Bibliographic Details
Published in:Breast cancer research and treatment 2007-01, Vol.101 (2), p.149-160
Main Authors: Brackenbury, William J, Chioni, Athina-Myrto, Diss, James K J, Djamgoz, Mustafa B A
Format: Article
Language:English
Subjects:
Blotting, Western
Breast cancer
Breast Neoplasms - genetics
Breast Neoplasms - metabolism
Breast Neoplasms - pathology
Cancer research
Cell adhesion & migration
Cell Line, Tumor
Cell Movement - drug effects
Cell Movement - genetics
Cells
Female
Humans
Image Processing, Computer-Assisted
Immunohistochemistry
In Vitro Techniques
Infant, Newborn
Membranes
Microscopy, Confocal
Muscle Proteins - drug effects
Muscle Proteins - genetics
Muscle Proteins - metabolism
NAV1.5 Voltage-Gated Sodium Channel
Neoplasm Invasiveness - genetics
Oncology
Patch-Clamp Techniques
Protein Isoforms
Reverse Transcriptase Polymerase Chain Reaction
Ribonucleic acid
RNA
RNA, Small Interfering
Sodium Channel Blockers - pharmacology
Sodium Channels - drug effects
Sodium Channels - genetics
Sodium Channels - metabolism
Tetrodotoxin - pharmacology
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Summary:Upregulation of functional voltage-gated Na+ channels (VGSCs) occurs in metastatic human breast cancer (BCa) in vitro and in vivo. The present study aimed to ascertain the specific involvement of the "neonatal" splice variant of Nav1.5 (nNav1.5), thought to be predominant, in the VGSC-dependent invasive behaviour of MDA-MB-231 cells. Functional activity of nNav1.5 was suppressed by two different methods targeting nNav1.5: (i) small interfering RNA (siRNA), and (ii) a polyclonal antibody (NESO-pAb); effects upon migration and invasion were determined. nNav1.5 mRNA, protein and signalling were measured using real-time PCR, Western blotting, and patch clamp recording, respectively. Treatment with the siRNA rapidly reduced (by approximately 90%) the level of nNav1.5 (but not adult Nav1.5) mRNA, but the protein reduction was much smaller (approximately 30%), even after 13 days. Nevertheless, the siRNA reduced peak VGSC current density by 33%, and significantly increased the cells' sensitivity to nanomolar tetrodotoxin (TTX). Importantly, the siRNA suppressed in vitro migration by 43%, and eliminated the normally inhibitory effect of TTX. Migrated MDA-MB-231 cells expressed more nNav1.5 protein at the plasma membrane than non-migrated cells. Furthermore, NESO-pAb reduced migration by up to 42%, in a dose-dependent manner. NESO-pAb also reduced Matrigel invasion without affecting proliferation. TTX had no effect on cells already treated with NESO-pAb. It was concluded that nNav1.5 is primarily responsible for the VGSC-dependent enhancement of invasive behaviour in MDA-MB-231 cells. Accordingly, targeting nNav1.5 expression/activity may be useful in clinical management of metastatic BCa.
ISSN:0167-6806
1573-7217
DOI:10.1007/s10549-006-9281-1