The Impact of Epithelial Sodium Channel on Breast Cancer Cell Migration

Abstract

Breast cancer is the most common cancer in New Zealand women, with the majority of breast cancer deaths being due to metastasis. This highlights the importance of identifying regulators and, thus, potential therapeutic targets, of breast cancer metastasis. Ion channel dysregulation may be crucial in cancer development via the regulation of cancer cell characteristics such as migration, invasion and proliferation. Ion channels, such as the epithelial sodium channel (ENaC), may regulate the important process for metastasis development of epithelial-mesenchymal transition (EMT), which involves a change of cell phenotype whereby cells lose their epithelial characteristics and exhibit a more migratory phenotype. There is limited research investigating the role of ENaC in breast cancer or the effect of ENaC on EMT. Therefore, the aim of this research is to investigate the role of ENaC in the migration of post-EMT breast cancer cells and the changes in mRNA levels of ENaC subunits and EMT markers. Two established forms of migration assay, Scratch and Boyden chamber, were used with two post-EMT breast cancer cell lines: BT549 and MDAMB231. Amiloride was used to block the activity of ENaC, and aldosterone was used to increase the expression of ENaC and the effect on breast cancer cell migration was observed. RT-qPCR was used to examine changes in ENaC subunit mRNA levels or markers of EMT following treatment with amiloride or aldosterone. When ENaC was blocked with amiloride, cell migration was significantly decreased in both cell lines in both scratch assays at 12 hrs (n = 4, p < 0.01). A reduction in cell migration was also observed in the Boyden chamber assay for the MDAMB231 cell line (n = 6, p < 0.05). When ENaC expression was increased with aldosterone, the two cell lines showed significantly enhanced migration ability in Boyden chamber assays (n = 8, p < 0.05). In the scratch assay, the BT549 cell line showed significantly enhanced migration at 12 hrs (n = 6, p < 0.05), whereas the MDAMB231 cell line had a reduced cell migration with aldosterone which was the same effect observed with amiloride. No noteworthy changes were observed in mRNA level of ENaC subunits or EMT markers following amiloride or aldosterone treatment. Altogether, these results indicate that ENaC has a role in the migration of breast cancer cells. The results of this project highlight ENaC as a potential therapeutic target for inhibiting the spread of breast cancer and improving the prognosis for breast cancer patients.