The Role of α-ENaC and δ-ENaC in Breast Cancer Cell Migration

Abstract

Breast cancer is an important disease worldwide, primarily affecting women, and is the most common and deadliest form of female cancer. This is reflected in New Zealand’s population as breast cancer has high incidence and mortality rates. In New Zealand, almost 700 deaths occur each year due to breast cancer, with a majority due to metastases.

The progression of cancer into a metastatic disease requires a change in cell phenotype, possibly through a process called epithelial-to-mesenchymal transition (EMT). When EMT occurs, fully epithelial cells, with cell to cell junctions and apical-basolateral polarity, transition into cells with a mesenchymal phenotype, becoming more invasive and motile and changing their morphology. Ion channels are reported to be important regulators of EMT including some evidence for a role of the epithelial sodium channel (ENaC). ENaC mRNA expression has been correlated with prognosis in breast cancer patients. Aldosterone, which increases ENaC mRNA and protein in other tissue, has been shown to alter breast cancer cell migration. This suggests that ENaC may have a role in breast cancer cell migration.

The aims of this project were to understand the role of α-ENaC and δ-ENaC in breast cancer cell migration by increasing and decreasing their expression within the cells. My hypotheses were “overexpression of α-ENaC or δ-ENaC will cause an increase in breast cancer cell migration” and “knockdown of α-ENaC or δ-ENaC will cause a decrease in breast cancer cell migration”.

Two breast cancer cell lines, BT-549 and MDA-MB-231, were used in this project to model breast cancer cell migration. These cells were transfected to either overexpress or knockdown α-ENaC or δ-ENaC. Scratch assays were then performed to quantify any changes in migration speed of the cells. The cells were then lysed and underwent qPCR to validate the overexpression or knockdown. To compare the role of ENaC in breast cancer cell migration, a two-way ANOVA was performed.

Overexpression or knockdown of α-ENaC in MDA-MB-231 and BT-549 cells did not significantly alter migration of the cells compared to control cells. Results from qPCR analysis showed successful overexpression of α-ENaC. Similarly, overexpression or knockdown of δ-ENaC in MDA-MB-231 and BT-549 cells did not significantly alter migration of the cells. Results from the qPCR showed overexpression of δ-ENaC in both cell lines was successful. Results from qPCR experiments have shown that attempts to knockdown of α-ENaC and δ-ENaC were unsuccessful in both cell lines.

The results did not support the hypothesis that altering levels of α-ENaC or δ-ENaC would change the rate of breast cancer cell migration, although a second migration assay should be used to confirm these results. Therefore, ENaC may be regulating another pathway, such as proliferation, to contribute to EMT.