SCN5A and breast cancer: While there are several subtypes of VGSC found upregulated in a number of carcinomas, breast cancer in particular, there is distinctively high expression of the ‘neonatal’ splice variant of the cardiac VGSC isoform, Nav1.5 (nNav1.5) that potentiates motility, migration, and invasion of aggressive human breast cancer cells in vitro and metastasis in vivo [10].