SLC5A4 and breast cancer: The sodium transporter subtypes examined were the VGSCs subtype Nav1.5, which is known to be upregulated in clinical breast cancer cases and in MDA-MB-231 cells, Na,K-ATPase α1, a ubiquitously expressed subtype of sodium pumps in human cells, and Na,K-ATPase α3, a subtype typically found in neurons among other specialized cells.