P0230 Characterisation of VGSC and rest expression, and possible interaction, in human breast cancer cell lines with different metastatic potential

Abstract

Background Voltage-gated sodium channels (VGSCs) are a hallmark molecule of excitable cells, such as neurons and cardiac cells. In metastatic human breast cancer, upregulation of VGSCs has been associated with mediation of metastatic cellular behaviours in vitro and in vivo. Abnormal expression of VGSCs in several epithelial-origin tumours, such as breast cancer, prostate cancer, and lung cancer, suggests that these cancers harbour defects in regulators for excitable cells. One such regulator is the repressor element silencing transcription factor (REST). REST has been reported to exhibit tumour-suppressor function, and its impaired function and lack of expression in cancers has been linked with aggressive phenotype. In this study, REST and VGSC expression was characterised in human breast cancer cell lines with different metastatic potential, and possible interactions were elucidated. Methods REST and VGSC (Nav1.5 and nNav1.5) expression was compared between non-cancerous (MCF-10A), weakly metastatic (MCF-7), and aggressive human breast cancer cell lines (MDA-MB-231). Conventional and semi-quantitative real-time PCR was used to validate the primers and measure gene expressions of the target genes. Western blot was done to determine REST protein expression. Findings Nav1.5 and nNav1.5 mRNA expression was 140-fold and 40-fold greater, respectively, in MDA-MB-231 cells compared with MCF-7 cells, and no expression was detected in MCF-10A cells. REST mRNA was detected in all three cell lines, with the highest expression in MCF-7 cells; expression was 1.9-fold higher in MCF-7 and 0.2-fold lower in MDA-MB-231 cells than in MCF-10A cells. REST mRNA expression was 0.6-fold lower in MDA-MB-231 cells than in MCF-7 cells. REST protein was expressed in all three cell lines. Similar to mRNA expression, REST protein expression was highest in MCF-7 cells and lowest in MDA-MB-231 cells. Interpretation This study showed a lack of REST expression in VGSC-upregulated, aggressive breast cancer cells, suggesting possible upstream interaction or regulation of REST with VGSC expression in breast cancer.