Abstract
Breast cancer is currently the leading cause of cancer death in women globally, including New Zealand. Metastatic breast cancer contributes to 90% of these cancer-associated deaths, where breast tumour cells spread to distant organs. Unfortunately, there are still no globally effective therapies targeted to TNBC despite the advancement of cancer treatment. The progression and metastasis of breast cancer is highly regulated by a process called epithelial mesenchymal plasticity (EMP). EMP is a process where cancer cells lose their epithelial phenotypes and transition into mesenchymal cells with increase proliferation, migratory capability and apoptosis resistant. Ion channels, including the epithelial sodium channel (ENaC) that consists of an α, β and γ subunit, have been shown to regulate EMP and cancer progression. Previous research from our lab has indicated that αENaC can exhibit a protective role against breast cancer, where αENaC overexpression resulted in reduced cell proliferation and improved survival, potentially via EMP. However, the underlying signalling pathway of how αENaC affects EMP and breast cancer progression has not been thoroughly investigated. Therefore, this project aimed to investigate the mechanism of how αENaC affects breast cancer proliferation.
Cell cycle analysis using flow cytometry showed there was an accumulation of cells in the G0/G1 phase when compared between control and αENaC overexpressing cells (N = 5; P < 0.05). Previous work has identified that there was a significant difference in the mRNA levels of EGFR comparing between the αENaC overexpressing and control MDA-MB-231 cells. Therefore, EGFR mRNA expression was determined using RT-qPCR and the result showed an increased EGFR mRNA expression (N = 6, P < 0.05).
Previous research has shown that EGFR activation (pEGFR) can initiate cell apoptosis via STAT1. Therefore, this was investigated further by performing Western blot analysis on pEGFR comparing between the control and αENaC overexpressing cells. The result showed activation in both cell conditions but no significant changes between them (N = 4; P > 0.05). Additionally, RT-qPCR was performed on the mRNA expression of STAT1, and the result showed increased STAT1 expression (N = 6; P < 0.01).
Altogether, the results of this Masters project provide an insight into the link between αENaC and breast cancer cell proliferation. A potential signalling pathway was proposed that αENaC lead to the reduced cell proliferation and potentially increased cell apoptosis via EGFR-STAT1 signalling pathway. The work presented here also highlighted ENaC as a potential target for future breast cancer therapies, however further research is required to confirm this.