In the past 20 years, there are encouraging reports on the up-regulation of voltage-gated sodium channels (VGSCs) in human carcinomas. Particularly in the aggressive breast cancer, MDA-MB-231 cells, the cardiac isoform Nav1.5 and its neonatal splice variant, nNav1.5 are found to be responsible in mediating its aggressiveness. Subsequently, investigating the compendium factors that contribute to the up-regulation of Nav1.5/nNav1.5 in breast cancer will expand our understanding on metastasis which has contributed to 90% of mortality among cancer patients. Previously, growth factors, hormones, auxiliary ß-subunits and Na+ concentration are demonstrated to regulate VGSCs expression in breast cancer. Transcription factor is another potential feature that could regulate gene expression. In particular, repressor element silencing transcription factor, REST is reported to play a role in silencing the expression of VGSCs in normal epithelial cells whilst loss/lacking of REST expression have been shown to predispose cells to transformation. Herein, the role of REST in regulating the expression of Nav1.5/nNav1.5 was investigated.
Small interfering RNA (siRNA) was utilized to transiently down-regulate REST expression in the weakly metastatic MCF-7 cells, which lack Nav1.5/nNav1.5. The effect of siRNA on Nav1.5/nNav1.5 mRNA expression was measured by real-time PCRs. Immunoprecipitation (IP) followed by EMSA was also conducted to investigate the interaction of the two molecules.
siRNA-REST did not alter the mRNA expression of Nav1.5 and nNav1.5 in MCF-7 cells. However, the IP-EMSA experiments indicated that there was a possible physical interaction between REST protein and Nav1.5 DNA-promoter sequence.
Aberrant expression of transcription factor, REST involved in the mechanisms of VGSCs up-regulation in aggressive breast cancer though from the results of siRNA and IP-EMSA experiments, the complexity of the interaction are more than just direct interaction.
Clinical trial identification
All authors have declared no conflicts of interest.