The effect of nNav1.5 gene expression in breast cancer metastasis

Abstract

Breast cancer is the most common cancer among women. Its metastasis is lethal that can not be detected at microscopic levels using current techniques. Thus, there is need for reliable early metastasis markers. Neonatal Nav1.5 (nNav1.5) is a voltage-gated sodium channel (VGSC) and one of the potential early markers for breast cancer metastasis. In this study, we determined that nNav1.5 expression was in parallel with breast cancer metastasis and estrogen receptor (ER) expression in a group of patients. To provide data for future drug development, we analyzed the expression pattern of nNav1.5 protein in normal human tissues. The protein was not expressed in skeletal and heart muscle, brain, small intestine, colon, stomach, esophagus, urinary bladder and prostate but expressed in breast at basal level. We also investigated the distribution of VGSC in these non-excitable human tissues. Except urinary bladder, VGSC protein was determined mostly in secretory cells in all of the tissues above that may indicate a role in secretion. Upon identification of VGSC upregulation in tumor regions of different cancers including, colon, stomach, urinary bladder, kidney and lung it is possible that VGSC expression could be a widespread mechanism in cancer metastasis. Within the scope of this thesis, we also investigated the possible role of estrogen on nNav1.5 upregulation and activity in metastatic breast cancer. Estrogen had no effect on proliferation of cells but slightly increased motility through nNav1.5 in highly metastatic cells that express the protein. In weakly metastatic cells that do not posses nNav1.5, estrogen decreased motility slightly. The quantity of nNav1.5 protein was not affected by estrogen but functionally available form on the plasma membrane was increased only in the highly metastatic cells. These results may suggest that estrogen increases motility capacity of breast cancer cells by regulating nNav1.5 activity.