SCN9A and cancer: The involvement of VGSCs in human cancer invasion and growth has been well documented; for example while NaV1.5 has been attributed to the migration and invasion in metastatic breast cancer (Yang et al., 2012), NaV1.7 is now known to be a novel marker for human prostate cancer (Brackenbury & Djamgoz, 2006; Diss et al., 2005) and VGSCs may play a role in the metastatic behaviour of cancer cells (Patel & Brackenbury, 2015).